Stages Of Leaf Development Research Articles

Transcriptional profiling of catechins biosynthesis genes during tea plant leaf development.

A total of 299,113 unigenes were generated and 15,817 DEGs were identified. We identified candidate genes associated with the regulation of catechins biosynthesis during leaf development in tea plant. The tea plant (Camellia sinensis (L.) O. Kuntze) is one of the most economically significant crops worldwide because of its positive effects on human health. The health benefits of tea are mainly attributed to catechins, which are the predominant polyphenols that accumulate in tea. Catechins are products of the phenylpropanoid and flavonoid biosynthetic pathways. Although catechins were identified in tea leaves long ago, the molecular mechanisms regulating catechins biosynthesis remain unclear. To identify candidate genes involved in catechins biosynthesis, we analyzed the transcriptomes of tea leaves during five different leaf stages of development using RNA-seq. Approximately 809 million high-quality reads were obtained, trimmed, and assembled into 299,113 unigenes with an average length of 565bp. A total of 15,817 unigenes were differentially expressed during the different stages of leaf development. These differentially expressed genes were enriched in a variety of processes such as the regulation of the cell cycle, starch and sucrose metabolism, photosynthesis, phenylpropanoid biosynthesis, phenylalanine metabolism, and flavonoid biosynthesis. Based on their annotations, 51 of these differentially expressed unigenes are involved in phenylpropanoid and flavonoid biosynthesis. Furthermore, transcription factors such as MYB, bHLH and MADS, which may involve in the regulation of catechins biosynthesis, were identified through co-expression analysis of transcription factors and structural genes. Real-time PCR analysis of candidate genes indicated a good correlation with the transcriptome data. These findings increase our understanding of the molecular mechanisms regulating catechins biosynthesis in the tea plant.

The effects on in vitro digestibility from different developmental stages of silkworm larvae, Bombyx mori (Lepidoptera: Bombycidae) and position of mulberry leaves, Morus alba (Rosales: Moraceae)

Mulberry leaves (Morus alba var. Buriram 60) at the positions 1, 2, 3, 4 and 5 were harvested from 2nd, 3rd, 4th, 5th–6th and 7th–8th below the primordia, respectively; to evaluate on in vitro digestibility of carbohydrate (IVCD) and protein (IVPD) by using the crude enzyme extract from whole body of 3rd to 5th instar larva of mulberry silkworm (Bombyx mori). The crude enzymes were extracted from the whole body of larva against the reviewed data of gut extract from the previous studies. The optimal temperature and pH was similar between whole body and gut extracts, indicating the possible use of whole body for in vitro digestibility study. There was no statistical interaction between leaf position and developmental stage of larva. In all stages of larva, the leaf positions 2 and 3 were higher in IVCD than in the other positions (p<0.05), whereas the lowest IVPD was found in position 1 (p<0.05). The IVCD was highest in 3rd instar larva (p<0.001) while the decrease trend of IVPD was observed in 4th, 3rd and 5th stages (p<0.001), respectively. Based on the digestibility values, the preferred leaf positions for the mulberry silkworm instar larvae (3rd–5th) were leaf positions 2 and 3. This in vitro screening of the leaf supports the development of an artificial mulberry leaf-based diet for B. mori used in sericulture.

BIG LEAF is a regulator of organ size and adventitious root formation in poplar.

Here we report the discovery through activation tagging and subsequent characterization of the BIG LEAF (BL) gene from poplar. In poplar, BL regulates leaf size via positively affecting cell proliferation. Up and downregulation of the gene led to increased and decreased leaf size, respectively, and these phenotypes corresponded to increased and decreased cell numbers. BL function encompasses the early stages of leaf development as native BL expression was specific to the shoot apical meristem and leaf primordia and was absent from the later stages of leaf development and other organs. Consistently, BL downregulation reduced leaf size at the earliest stages of leaf development. Ectopic expression in mature leaves resulted in continued growth most probably via sustained cell proliferation and thus the increased leaf size. In contrast to the positive effect on leaf growth, ectopic BL expression in stems interfered with and significantly reduced stem thickening, suggesting that BL is a highly specific activator of growth. In addition, stem cuttings from BL overexpressing plants developed roots, whereas the wild type was difficult to root, demonstrating that BL is a positive regulator of adventitious rooting. Large transcriptomic changes in plants that overexpressed BL indicated that BL may have a broad integrative role, encompassing many genes linked to organ growth. We conclude that BL plays a fundamental role in control of leaf size and thus may be a useful tool for modifying plant biomass productivity and adventitious rooting.

A mobile NMR lab for leaf phenotyping in the field

BackgroundLow field NMR has been used to investigate water status in various plant tissues. In plants grown in controlled conditions, the method was shown to be able to monitor leaf development as it could detect slight variations in senescence associated with structural modifications in leaf tissues. The aim of the present study was to demonstrate the potential of NMR to provide robust indicators of the leaf development stage in plants grown in the field, where leaves may develop less evenly due to environmental fluctuations. The study was largely motivated by the need to extend phenotyping investigations from laboratory experiments to plants in their natural environment.MethodsThe mobile NMR laboratory was developed, enabling characterization of oilseed rape leaves throughout the canopy without uprooting the plant. The measurements made on the leaves of plants grown and analyzed in the field were compared to the measurements on plants grown in controlled conditions and analyzed in the laboratory.ResultsThe approach demonstrated the potential of the method to assess the physiological status of leaves of plants in their natural environment. Comparing changes in the patterns of NMR signal evolution in plants grown under well-controlled laboratory conditions and in plants grown in the field shows that NMR is an appropriate method to detect structural modifications in leaf tissues during senescence progress despite plant heterogeneity in natural conditions. Moreover, the specific effects of the environmental factors on the structural modifications were revealed.ConclusionThe present study is an important step toward the selection of genotypes with high tolerance to water or nitrogen depletion that will be enabled by further field applications of the method.

TCP family genes control leaf development and its responses to hormonal stimuli in tea plant [Camellia sinensis (L.) O. Kuntze

Tea plant [Camellia sinensis (L.) O. Kuntze] is a perennial evergreen woody crop that is cultivated worldwide. Tea leaf is an important resource for producing natural non-alcoholic beverages. TCP (TEOSINTE BRANCHED1/CYCLOIDEA/PROLIFERATING CELL FACTORS) is a transcription factor family that controls the cell growth and proliferation of leaf tissues. In this study, 17 homologous TCP family transcription factors were identified and characterized in the leaf transcriptome of C. sinensis. The structural features, phylogenetic tree, and interaction networks of C. sinensis TCP (CsTCP) proteins were analyzed. Prediction of miRNA target sites suggests that miR319 may be involved in the post-transcriptional regulation of the CsTCP15 transcript. The expression profiles of all identified CsTCP genes were investigated in five tea leaf developmental stages (i.e., 1st, 2nd, 3rd, 4th, and older leaves) and normal growth tea leaves subjected to five hormonal stimuli (i.e., ABA, GA3, IAA, MeJA, and SA). Several CsTCP genes presented functional redundancies in leaf development and response to hormones. This study establishes an extensive overview of the TCP family genes and provides insights into the molecular mechanism of leaf development and hormonal stimuli in C. sinensis.

Distribution of 14C-Photosynthetate in the Shoot of Vitis vinifera L. cv Cabernet Sauvignon I. The Effect of Leaf Position and Developmental Stage of the Vine

The distribution of photosynthetates, originating in leaves of different parts of the shoot of Vi tis vinifera L. cv Cabernet Sauvignon at berry set, pea size, veraison and ripeness stages, was investigated. Specific photosynthetic activity of the CO,-treated leaves gradually decreased during the season. Photosynthetates were hoarded in the leaves at berry set, but were increasingly diverted to the bunches after that. The apical leaves displayed the Itlghes.t.photosynthesis. The leaves opposite and below the bunches accumulated very little photosynthetafes, especially from veraison to ripeness. Redistribution of photosynthetates among the basal, middle and apical leaves was generally very restricted at all stages. Multidirectional distribution from the site of application of 14CO, occurred at berry set stage, while from pea size to ripeness photosynthetates were mainly translocated basipetally. Highest accumulation in the bunches occurred at veraison, while the basal leaves were primarily used to nourish the bunch.

Concentration and retention of chlorophyll around the extrafloral nectary of Mallotus japonicus.

Plants need to allocate some of their limited resources for defense against herbivores as well as for growth and reproduction. However, the priority of resource allocation within plants has not been investigated. We hypothesized that plants with extrafloral nectaries (EFNs) invest more chlorophyll around their EFNs—to support a high rate of carbon fixation there—than in other leaf parts of young leaves. Additionally, this chlorophyll may remain around EFNs rather than in the other leaf parts. We used Mallotus japonicus plants to investigate the chlorophyll content at leaf centers and edges and around EFNs at four stages of leaf development: middle‐expanded young leaves, fully expanded mature leaves, senior leaves, and leaves prior to abscission. These four stages of development were located at the third, fifth, eighth, and eleventh leaf positions from the apex, respectively. The results revealed that the chlorophyll content around the EFN side of the third‐position leaves was higher than that at the leaf center or edge. Although the chlorophyll content in the fifth‐position leaves did not differ between those at the leaf edge and around EFNs, the chlorophyll content around EFNs in the eighth‐position leaves was higher than that at the leaf centre and edge. The volume of EF nectar was positively correlated with the chlorophyll content around EFN during the leaf stage, but it was not correlated with the chlorophyll content in the leaf center and edge, except in fifth‐position leaves. These findings suggest that M. japonicus plants facilitate and maintain secretion of EF nectar in their young and old leaves, respectively, through the concentration and retention of chlorophyll around EFNs.

The transition time from the juvenile phase to the adult phase differs in soybean cultivars ‘Enrei’ and ‘Peking’

AbstractPlants develop juvenile phase to adult phase in vegetative stage. Although soybean is a very important crop worldwide, there has been only one study of the juvenile–adult phase change. In this study, we determined that the juvenile–adult phase change occurred at different stages in two soybean cultivars that differ in their photosensitivity. Cultivar ‘Enrei’ (E1e2e3E4) is weakly photosensitive and cultivar ‘Peking’ (E1E2E3E4) is strongly photosensitive. In ‘Enrei’, the leaf size gradually increased at a constant leaf position regardless of the difference in day length. In ‘Peking’ plants transferred to short‐day conditions at several leaf development stages, leaf size gradually increased at different leaf positions. Expression of miR156 by ‘Enrei’ transferred to short‐day conditions had nearly the same pattern as that of ‘Enrei’ grown under long‐day conditions. In ‘Peking’, the expression of miR156 had different patterns in younger leaves of plants subjected to either a short‐day treatment or long‐day conditions. These results indicate that the E2 and E3 loci that regulate photosensitivity also regulate the expression of miR156 and the juvenile–adult phase change in soybean.

Mineral Content Differs among Microgreen, Baby Leaf, and Adult Stages in Three Cultivars of Kale

Kale (Brassica oleracea L. and other species) is considered a rich source of important minerals. Kale at the early stage of leaf development is assumed to contain higher levels of minerals than at maturity. However, literature supporting this assumption is scarce. In this study, the concentrations of macronutrients [potassium (K), calcium (Ca), magnesium (Mg), and phosphorus (P)] and micronutrients [sodium (Na), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu)] either essential to plant growth and development, or important to human health, were determined. Three kale cultivars (green leaf ‘Dwarf Blue Curled’ and red leaf ‘Scarlet’ in B. oleracea, and green leaf with purple midvein ‘Red Russian’ in Brassica napus) were evaluated at five different leaf developmental stages; cotyledon [microgreen 1 (MG1)], two true leaf [microgreen 2 (MG2)], four true leaf [baby leaf 1 (BL1)], six true leaf [baby leaf 2 (BL2)], and adult. As kale matured, total mineral (ash) decreased from 14.6–19.1% at the microgreen stages to 3.9–6.4% at the adult stage, on a dry weight (DW) basis. Microgreen kale contained higher concentrations of most minerals than adult kale, on a DW basis, in all cultivars. On a fresh weight (FW) (as consumed) basis, the highest level of total mineral concentration was detected at baby leaf stage 1 (1.3–1.7%) and there was no difference between microgreen and adult stages. Fresh microgreens generally contained lower K, Ca, Mg, Fe, and Zn than fresh baby leaves, and lower concentrations of Ca and Mg and higher Na compared with fresh adult kale. Overall, water content deceased from 95.1% at MG1 stage to 80.0% at adult stage. The variation in water content and mineral accumulation during leaf development might contribute to the discrepancy. In addition, fresh leaves of ‘Scarlet’ contained higher concentration of total minerals than that of ‘Dwarf Blue Curled’ or ‘Red Russian’. Although ‘Dwarf Blue Curled’ and ‘Red Russian’ are different species, their mineral content profile during leaf development was similar. Together, cultivar and leaf developmental stage influenced mineral content in kale.

Comparative Performance of Three Tropical Turfgrasses Digitaria longiflora, Axonopus compressus and St. Augustinegrass under Simulated Shade Conditions

Shade affects turf quality by reducing light for photosynthesis. The shade tolerance of the tropical grasses, Digitaria longiflora and Axonopus compressus were evaluated against Stenotaphrum secundatum (St. Augustinegrass). The grasses were established under shade structures that provide 0%, 50%, 75% or 90% shade level for 30 days. A suite of leaf traits, recorded from similar leaf developmental stage, displayed distinct responses to shade conditions. Leaf length, relative to control, increased in all three species as shade level increased. The mean leaf extension rate was lowest in St. Augustinegrass (80.42%) followed by A. compressus (84.62%) and D. longiflora (90.78%). The higher leaf extension rate in D. longiflora implied its poor shade tolerance. Specific leaf area (SLA) increased in all species with highest mean SLA increase in D. longiflora (348.55 cm2 mg−1) followed by A. compressus (286.88 cm2 mg−1) and St. Augustinegrass (276.28 cm2 mg−1). The highest SLA increase in D. longiflora suggested its lowest performance under shade. The percent green cover, as estimated by digital image analysis, was lowest in D. longiflora (53%) under 90% shade level compared to both species. The relative shade tolerance of the three turfgrasses could be ranked as St. Augustinegrass > A. compressus > D. longiflora.

Evaluation of parameters affecting Agrobacterium-mediated transient expression in citrus

Agrobacterium-mediated transient expression assays are a convenient alternative to stable expression because they are simple, easy to perform, and achieve gene expression rapidly. This study investigated the factors affecting transient gene expression efficiency in citrus by observing the cryo-sectioning of leaf samples under a laser confocal microscope. These factors included the composition of the infiltration buffer, the Agrobacterium cell density, the leaf development stage, the incubation temperature, and plant genotype. The highest transient expression level of yellow fluorescent protein (YFP) was detected in Mexican lime (Citrus aurantifolia) on the third day after the intermediate-aged leaves were infiltrated with the improved infiltration buffer 1 (15 mmol L−1 2-(N-morpholino) ethanesulfonic acid, 10 mmol L−1 MgCI2, and 200 pmol L−1 acetosyringone), which had an optical density of 0.8 and was incubated at 22°C. Additionally, this transient expression assay was applied to other citrus genotypes. Of note, trifoliate orange (Poncirus trifoliata) and kumquat (Fortunella obovate) had higher expression efficiency than other six genotypes of the Citrus genus. Our study provides research basis for the selection of optimization strategies in transient gene expression and improves the method for available genome investigation in citrus.

Digital Gene Expression Analysis Provides Insight into the Transcript Profile of the Genes Involved in Aporphine Alkaloid Biosynthesis in Lotus (Nelumbo nucifera).

The predominant alkaloids in lotus leaves are aporphine alkaloids. These are the most important active components and have many pharmacological properties, but little is known about their biosynthesis. We used digital gene expression (DGE) technology to identify differentially-expressed genes (DEGs) between two lotus cultivars with different alkaloid contents at four leaf development stages. We also predicted potential genes involved in aporphine alkaloid biosynthesis by weighted gene co-expression network analysis (WGCNA). Approximately 335 billion nucleotides were generated; and 94% of which were aligned against the reference genome. Of 22 thousand expressed genes, 19,000 were differentially expressed between the two cultivars at the four stages. Gene Ontology (GO) enrichment analysis revealed that catalytic activity and oxidoreductase activity were enriched significantly in most pairwise comparisons. In Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, dozens of DEGs were assigned to the categories of biosynthesis of secondary metabolites, isoquinoline alkaloid biosynthesis, and flavonoid biosynthesis. The genes encoding norcoclaurine synthase (NCS), norcoclaurine 6-O-methyltransferase (6OMT), coclaurine N-methyltransferase (CNMT), N-methylcoclaurine 3′-hydroxylase (NMCH), and 3′-hydroxy-N-methylcoclaurine 4′-O-methyltransferase (4′OMT) in the common pathways of benzylisoquinoline alkaloid biosynthesis and the ones encoding corytuberine synthase (CTS) in aporphine alkaloid biosynthetic pathway, which have been characterized in other plants, were identified in lotus. These genes had positive effects on alkaloid content, albeit with phenotypic lag. The WGCNA of DEGs revealed that one network module was associated with the dynamic change of alkaloid content. Eleven genes encoding proteins with methyltransferase, oxidoreductase and CYP450 activities were identified. These were surmised to be genes involved in aporphine alkaloid biosynthesis. This transcriptomic database provides new directions for future studies on clarifying the aporphine alkaloid pathway.

Leaf traits and photosynthetic responses of Betula pendula saplings to a range of ground-level ozone concentrations at a range of nitrogen loads

Ground-level ozone (O3) concentrations and atmospheric nitrogen (N) deposition rates have increased strongly since the 1950s. Rising ground-level O3 concentrations and atmospheric N deposition both affect plant physiology and growth, however, impacts have often been studied in isolation rather than in combination. In addition, studies are often limited to a control treatment and one or two elevated levels of ozone and/or nitrogen supply. In the current study, three-year old Betula pendula saplings were exposed to seven different O3 profiles (24h mean O3 concentration of 36–68ppb in 2013, with peaks up to an average of 105ppb) in precision-controlled hemispherical glasshouses (solardomes) and four different N loads (10, 30, 50 or 70kgNha−1y−1) in 2012 and 2013. Here we report on the effects of enhanced O3 concentrations and N load on leaf traits and gas exchange in leaves of varying age and developmental stage in 2013. The response of leaf traits to O3 (but not N) vary with leaf developmental stage. For example, elevated O3 did not affect the chlorophyll content of the youngest fully expanded leaf, but it reduced the chlorophyll content and photosynthetic parameters in aging leaves, relatively more so later than earlier in the growing season. Elevated O3 enhanced the N content of senesced leaves prior to leaf fall, potentially affecting subsequent N cycling in the soil. Enhanced N generally stimulated the chlorophyll content and photosynthetic capacity. Whilst elevated O3 reduced the light-saturated rate of photosynthesis (Asat) in aging leaves, it did not affect stomatal conductance (gs). This suggests that photosynthesis and gs are not closely coupled at elevated O3 under-light saturating conditions. We did not observe any interactions between O3 and N regarding photosynthetic parameters (Vc,max, Jmax, Asat), chlorophyll content, gs, N content in senesced leaves and leaf number. Hence, the sensitivity of these leaf traits to O3 in young silver birch trees is neither reduced nor enhanced by N load.

Wplyw Tytanitu� na plon i elementy skladowe plonu bardzo wczesnych odmian ziemniaka

The growing period for early potatoes is extremely short, only 50-80 days from planting to harvest. To obtain a high marketable tuber yield in such a short period good conditions for plant growth must be ensured. In modern agriculture, plant growth stimulants have been gaining increasing importance. Although titanium (Ti) is neither a major nor minor nutrient for plants, it is classified as a beneficial element for plant growth. This paper analyses the effect of dose (0.2 dm3*ha-1 or 0.4 dm3*ha-1) and date (leaf development stage – BBCH 14-16, tuber formation stage – BBCH 41-43, leaf development stage and tuber formation stage) of the application of Tytanit® (8.5 g Ti in 1 dm3) on the yield and yield components of very early-maturing potato cultivars (‘Lord’ and ‘Milek’). Potatoes were harvested 75 days after planting (the end of June). Tytanit® caused an increase in the tuber number and tuber weight per plant, particularly under stress conditions, although the effect of cultivars was not consistent. The growth stimulant did not have any effect on the average tuber weight. Following the application of Tytanit®, the total tuber yield was higher, on average, by 2.26 t*ha-1 (7.5%), and the marketable tuber yield (diameter above 30 mm) by 1.88 t*ha-1 (6.4%). The tuber number per plant was higher when Tytanit® was applied at the dose of 0.2 dm3*ha-1. Potato plants produced greatest tubers when Tytanit® was only applied in the leaf development stage (BBCH 1416). With double Tytanit® applications, i.e. in the leaf development stage and with repeated treatment in the tuber formation stage, both the tuber number and tuber weight per plant were lower. The Tytanit® application contributed to improved marketable value of the early potato yield due to a decreased share of small tubers (diameter below 40 mm) and an increased share of large tubers (diameter above 51 mm) especially in a year with a periodical water shortage in the tuber growth period. The examined very early-maturing potato cultivars showed a differential response to Tytanit®. The growth stimulant had a greater effect on the tuber number and tuber weight per plant for the ‘Lord’ cultivar. Following the Tytanit® application, the total tuber yield of ‘Lord’ cultivar was higher, on average by 3.71 t*ha-1 (12.7%) and marketable tuber yield by 3.22 t*ha-1 (11.4%). Tytanit® caused an increase in tuber yield of ‘Milek’ cultivar only in year with the highest air temperature and water shortage in June – the total tuber yield was higher, on average by 2.16 t*ha-1 (8.5%) and marketable tuber yield by 2.02 t*ha-1 (8.2%).

A Young Seedling Stripe2 phenotype in rice is caused by mutation of a chloroplast-localized nucleoside diphosphate kinase 2 required for chloroplast biogenesis.

Chloroplast development and chlorophyll (Chl) biosynthesis in plants are regulated by many genes, but the underlying molecular mechanisms remain largely elusive. We isolated a rice mutant named yss2 (young seedling stripe2) with a striated seedling phenotype beginning from leaf 2 of delayed plant growth. The mutant developed normal green leaves from leaf 5, but reduced tillering and chlorotic leaves and panicles appeared later. Chlorotic yss2 seedlings have decreased pigment contents and impaired chloroplast development. Genetic analysis showed that the mutant phenotype was due to a single recessive gene. Positional cloning and sequence analysis identified a single nucleotide substitution in YSS2 gene causing an amino acid change from Gly to Asp. The YSS2 allele encodes a NDPK2 (nucleoside diphosphate kinase 2) protein showing high similarity to other types of NDPKs. Real-time RT-PCR analysis demonstrated that YSS2 transcripts accumulated highly in L4 sections at the early leaf development stage. Expression levels of genes associated with Chl biosynthesis and photosynthesis in yss2 were mostly decreased, but genes involved in chloroplast biogenesis were up-regulated compared to the wild type. The YSS2 protein was associated with punctate structures in the chloroplasts of rice protoplasts. Our overall data suggest that YSS2 has important roles in chloroplast biogenesis.

New and sustainable essential oils obtained from the long-term explored cinnamomum-like Aniba canelilla

The traditional approach to extract the essential oils from precious-wood (Aniba canelilla), implies in obtaining it from the bark of the trunk of adult trees, usually resulting on the dead of the tree. In order to investigate the effect of seasonality, pruning and leaf development stages, essential oils from leaves and branches were obtained and the chemical composition analyzed by GC-FID and GC–MS. Multivariate analysis, PCA and HCA, allowed the distinction of three different types of essential oils from leaves and branches, with different chromatographic profiles. In general, 1-nitro-2-phenylethane contents were significantly higher in branches and have lower internal variation of this constituent than in leaves. The multivariate analysis also allowed the observation that seasonality and the stage of development did not influence the chemical composition of essential oils, as leaves and twigs were collected in different seasons, at different stages of development in the same area, are in a same group of similar chemical compositions, particularly characterized by the predominance of 1-nitro-2-phenylethane. Although variable, the levels of 1-nitro-2-phenylethane in leaves and twigs are comparable to the levels of 1-nitro-2-phenylethane observed in the stem wood and bark of A. canelilla. Thus, the extraction of essential oil of its leaves and branches may be an alternative way to prevent the overthrow of the trunk to produce essential oils of the specie.

Comprehensive investigation of tobacco leaves during natural early senescence via multi-platform metabolomics analyses.

Senescence is the final stage of leaf growth and development. Many different physiological activities occur during this process. A comprehensive metabolomics analysis of tobacco middle leaves at 5 different developmental stages was implemented through multi-platform methods based on liquid chromatography, capillary electrophoresis and gas chromatography coupled with mass spectrometry. In total, 412 metabolites were identified, including pigments, sterols, lipids, amino acids, polyamines, sugars and secondary metabolites. Dramatic metabolic changes were observed. Firstly, membrane degradation and chlorophyll down-regulation occurred after the 50% flower bud stage. Levels of major membrane lipids decreased, including those of the glycolipids in chloroplast thylakoids and phospholipids in membrane envelopes. Clear decreases in free sterols and acylated sterol glucosides were detected along with the accumulation of sterol esters. The accumulation of alkaloids was found. The amino acid levels were significantly decreased, particularly those of N-rich amino acids (glutamine and asparagine), thus reflecting N translocation. Subsequently, the antioxidant system was activated. Sugar alcohols and polyphenols accumulated when the lower leaves turned yellow. These results comprehensively revealed the metabolic changes that occur during tobacco leaf development and senescence under natural conditions.

Anatomy, photochemical activity, and DNA polymorphism in leaves of dwarf tomato irradiated with X-rays

The response of higher plants to ionising radiation depends on factors related to both radiation properties and plant features including species, cultivar, age, and structural complexity of the target organ. Adult plants of dwarf tomato were irradiated with different doses of X-rays to investigate possible variations in leaf morpho-anatomical traits, photosynthetic efficiency, and genomic DNA. In order to assess if and how responses depend on leaf developmental stage, we analysed two types of leaves; nearly mature leaves (L1) and actively developing leaves (L2), whose lamina size corresponded to 70 and 25 %, respectively, of the lamina size of the fully expanded leaves. The results show that the X-rays prevented full lamina expansion of the L2 leaves at all doses and induced early death of tissue of plants irradiated with doses higher than 20 Gy. Most anatomical modifications were not clearly dose-dependent and the radiation-induced increase in phenolic compounds was irrespective of dose. At high doses of X-rays (50 and 100 Gy), photochemical efficiency decreased significantly in both leaf types, whereas total chlorophyll content significantly decreased only in the L2 leaves. The random amplification of polymorphic DNA data show that the X-rays induced mutagenic effects in the L2 leaves even at low doses despite the absence of severe phenotypic alterations. Genetic structure found in the population of samples corroborates the results of anatomical and eco-physiological analyses: the 20 Gy dose seems to mark the threshold dose above which genetic alterations, structural anomalies, and perturbations in the photosynthetic apparatus become significant, especially in the actively expanding leaves.

Exploring drought stress-regulated genes in senna (Cassia angustifolia Vahl.): a transcriptomic approach.

De novo assembly of reads produced by next-generation sequencing (NGS) technologies offers a rapid approach to obtain expressed gene sequences for non-model organisms. Senna (Cassia angustifolia Vahl.) is a drought-tolerant annual undershrub of Caesalpiniaceae, a subfamily of Fabaceae. There are insufficient transcriptomic and genomic data in public databases for understanding the molecular mechanism underlying the drought tolerance of senna. Therefore, the main purpose of this study was to know the transcriptome profile of senna, with special reference to drought stress. RNA from two different stages of leaf development was extracted and sequenced separately using the Illumina technology. A total of 200 million reads were generated, and a de novo assembly of processed reads in the pooled transcriptome using Trinity yielded 43,413 transcripts which were further annotated using NCBI BLAST with "green plant database (txid 33090)," Swiss Prot, Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Groups (COG), and Gene Ontology (GO). Out of the total transcripts, 42,280 (95.0%) were annotated by BLASTX against the green plant database of NCBI. Senna transcriptome showed the highest similarity to Glycine max (41%), followed by Phaseolus vulgaris (16 %), Cicer arietinum (15 %), and Medicago trancatula (5 %). The highest number of GO terms were enriched for the molecular functions category; of these "catalytic activity" (GO: 0003824) (25.10 %) and "binding activity" (GO: 0005488) (20.10 %) were most abundantly represented. We used InterProscan to see protein similarity at domain level; a total of 33,256 transcripts were annotated against the Pfam domains. The transcripts were assigned with various KEGG pathways. Coding DNA sequences (CDS) encoding various drought stress-regulated pathways such as signaling factors, protein-modifying/degrading enzymes, biosynthesis of phytohormone, phytohormone signaling, osmotically active compounds, free radical scavengers, chlorophyll metabolism, leaf cuticular wax, polyamines, and protective proteins were identified through BLASTX search. The lucine-rich repeat kinase family was the most abundantly found group of protein kinases. Orphan, bHLH, and bZIP family TFs were the most abundantly found in senna. Six genes encoding MYC2 transcription factor, 9-cis-epoxycarotenoid dioxygenase (NCED), l -ascorbate peroxidase (APX), aminocyclopropane carboxylate oxidase (ACO), abscisic acid 8'-hydroxylase (ABA), and WRKY transcription factor were confirmed through reverse transcriptase-PCR (RT-PCR) and Sanger sequencing for the first time in senna. The potential drought stress-related transcripts identified in this study provide a good start for further investigation into the drought adaptation in senna. Additionally, our transcriptome sequences are the valuable resource for accelerated genomics-assisted genetic improvement programs and facilitate manipulation of biochemical pathways for developing drought-tolerant genotypes of crop plants.

Biochemical and transcriptomic analyses reveal different metabolite biosynthesis profiles among three color and developmental stages in 'Anji Baicha' (Camellia sinensis).

BackgroundThe new shoots of the albino tea cultivar ‘Anji Baicha’ are yellow or white at low temperatures and turn green as the environmental temperatures increase during the early spring. ‘Anji Baicha’ metabolite profiles exhibit considerable variability over three color and developmental stages, especially regarding the carotenoid, chlorophyll, and theanine concentrations. Previous studies focused on physiological characteristics, gene expression differences, and variations in metabolite abundances in albino tea plant leaves at specific growth stages. However, the molecular mechanisms regulating metabolite biosynthesis in various color and developmental stages in albino tea leaves have not been fully characterized.ResultsWe used RNA-sequencing to analyze ‘Anji Baicha’ leaves at the yellow-green, albescent, and re-greening stages. The leaf transcriptomes differed considerably among the three stages. Functional classifications based on Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes enrichment analyses revealed that differentially expressed unigenes were mainly related to metabolic pathways, biosynthesis of secondary metabolites, phenylpropanoid biosynthesis, and carbon fixation in photosynthetic organisms. Chemical analyses revealed higher β-carotene and theanine levels, but lower chlorophyll a levels, in the albescent stage than in the green stage. Furthermore, unigenes involved in carotenoid, chlorophyll, and theanine biosyntheses were identified, and the expression patterns of the differentially expressed unigenes in these biosynthesis pathways were characterized. Through co-expression analyses, we identified the key genes in these pathways. These genes may be responsible for the metabolite biosynthesis differences among the different leaf color and developmental stages of ‘Anji Baicha’ tea plants.ConclusionsOur study presents the results of transcriptomic and biochemical analyses of ‘Anji Baicha’ tea plants at various stages. The distinct transcriptome profiles for each color and developmental stage enabled us to identify changes to biosynthesis pathways and revealed the contributions of such variations to the albino phenotype of tea plants. Furthermore, comparisons of the transcriptomes and related metabolites helped clarify the molecular regulatory mechanisms underlying the secondary metabolic pathways in different stages.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0885-2) contains supplementary material, which is available to authorized users.