Shoot Apex Research Articles

Plasmodesmata callose binding protein 2 contributes to the regulation of cambium/phloem formation and auxin response during the tissue reunion process in incised Arabidopsis stem.

Plants are exposed to a variety of biotic and abiotic stresses, including wounding at the stem. The healing process (tissue reunion) begins immediately after stem wounding. The plant hormone auxin plays an important role during tissue reunion. In decapitated stems, auxin transport from the shoot apex is reduced and tissue reunion does not occur but is restored by application of indole-3-acetic acid (IAA). In this study, we found that plasmodesmata callose binding protein 2 (PDCB2) affects the expansion of the cambium/phloem region via changes in auxin response during the process of tissue reunion. PDCB2 was expressed in the cortex and endodermis on the incised side of stems 1-3 days after incision. PDCB2-knockout plants showed reduced callose deposition at plasmodesmata and DR5::GUS activity in the endodermis/cortex in the upper region of the incision accompanied by an increase in size of the cambium/phloem region during tissue reunion. In addition, PIN(PIN-FORMED)3, which is involved in lateral auxin transport, was induced by auxin in the cambium/phloem and endodermis/cortex in the upper part of the incision in wild type, but its expression of PIN3 was decreased in pdcb2 mutant. Our results suggest that PDCB2 contributes to the regulation of cambium/phloem development via auxin response.

Quantification of hormones and profiling of metabolites from vegetative to reproductive growth phase shift in Lagenaria siceraria (Molina) Standl

In the world of agricultural research, there has been a lot of emphasis on increasing insight into the decline of crop yield gap levels. Metabolomics is a relatively recent approach that aims to better understand the metabolic networks and is extensively being applied to agricultural research for its divergent growth and productivity by enhancing the behavior of plants under various stress. Lagenaria siceraria (Bottle gourd – Salad variety) has commonly been used because of its enormous nutritional, commercial, and medicinal benefits. The purpose of this investigation was to quantify the level of endogenous hormones and metabolites profiling at the vegetative and reproductive phase from various tissues of L. siceraria by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC–MS). The field-grown plant samples such as vegetative, male, and female flower-initiated parts including leaf, stem, tendril, and shoot apex were used for this study. The vegetative tissues had the highest level of trans zeatin and indole-3-acetic acid whereas indole-3-propanoic acid, trans zeatin, and gibberellic acid-3 were seen highest in the male flower-initiated tissues, and the level of IPA alone was found highest in the female flower-initiated tissues quantified by LC-MS/MS method. Additionally, N-Methyl-N-trimethylsilyl-trifluoroacetamide derivatized tissues showed the presence of astaxanthin and 1H-Indole, 2,3,5-trimethyl-1-(trimethylsilyl)- in vegetative tissues. On the contrary, kaur-16-ene-(8β,13β), an intermediate of GAs synthesis, gibberellic acid, and fumaric acid were recorded in reproductive tissues by GC–MS analysis. The first principal component analysis (PCA) biplot revealed two principal components that together accounted for 34.59 % and 22.96 % of the variance in the tissues of vegetative and reproductive phases respectively. In the second PCA biplot, the male and female flower-initiated tissues showed principal component levels of 42.94 % and 26.48 %, respectively. Also, the heat map analysis showed the fluctuation of phytohormone levels during both phases.

El rol del AIA y BAP en la regeneración y formación de brotes in vitro de tres variedades de fresa (Fragaria x ananassa Duch.)

The objective was to determine the response of three strawberrry varieties (Fragaria x ananassa Duch.) to the aplication of two plant growth regulators: indol acetic acid (IAA) and 6-Benzyl aminopurine (BAP) added to Murashige & Skoog médium in strawberry micropropagation. The complete randomized block design was used and three strawberry varieties ‘Aromas’, ‘Albion’ and ‘Camarosa’ were considered as trials. MS medium for shoot regeneration in initial stage was supplemented with BAP 0.5 mgL-1 and IAA 0.6 mgL-1. Shoot proliferation MS medium was supplemented with BAP 0.5 mgL-1 in multiplication stage and MS medium hormone free was used for rooting induction. It was determined that after 32 days of cultivation the combination of IAA and BAP significantly affected shoot regeneration of apical shoot tips of three strawberry varieties. The greatest effect was caused on ‘Camarosa’. In addition, results on shoot multiplication using BAP indicated that ‘Albion’ performed better in shoot proliferation in terms of shoots per explants reaching 2.51 compared to ‘Camarosa’ and ‘Aromas’ with significant differences. However rooting medium with no growth regulators improves root development with best response of ‘Camarosa’ root length reaching 4.76 cm.

In vitro Regeneration of Multiple Shoots in Abelmoschus esculentus (L.) Moench (Okra) via Apical Shoot Meristem Culture

Introduction: To develop the efficient protocol for multiple shoot regeneration of A.esculentus by apical root culture method. Abelmoschus esculentus L., commonly known as okra, is a member of the Malvaceae family, which is widely consumed due to its high nutrient content and potential therapeutic properties. Okra contains various bioactive compounds that ex-hibit antibacterial properties and may be useful in treating type-2 diabetes, digestive diseases, and liver detoxification. To select the plant for the present and prepare the efficient protocol for the development of multiple shoot regeneration culture method. Methods: In this study, we developed an efficient protocol for multiple shoot regeneration of A. esculentus using the apical shoot culture method. Mature shoot apex explants of the germinated A. esculentus genotype CoBhH1 were cultured on Murashige and Skoog (MS) medium supple-mented with different concentrations of cytokinins (BAP and TDZ) and auxins (IAA and NAA) to determine the optimal conditions for shoot induction. Results: The highest number of multiple shoots (27.04 shoots) was obtained with 0.8 mg/L TDZ. Excised shoots were cultured on MS medium supplemented with GA3, which induced elongation of the shoots to a maximum of 8-10 cm. Regenerated plantlets were successfully transferred to soil, with a 100% survival rate and no differences in morphology or growth characteristics com-pared to control plants. Rooting was achieved with 1 mg/L IBA. Conclusion: This study provides an efficient protocol for multiple shoot regeneration of A. esculentus through apical shoot culture, which has potential applications in plant breeding and genetic engineering.

Propagation of a U16 hybid Eucalyptus line by plant cell tissue culture

Eucalyptus is one of the important plant species for paper pulp, fuel wood, and timber. In this study, a hybrid Eucalyptus, U16 line, was investigated for rapid in vitro propagation. The apical and adventitious shoots served as initial explants. These were free-disease symptoms that were collected for surface sterilization. Different disinfectants including mercuric and Javel solutions at different concentrations and treated times were performed. The results showed that explants were cleaned under taping water with soap, rinsed in 70oEtOH for 1 minute, and then immersed in 10% Javen solution for 15 minutes and 0.1% HgCl2 for 10 minutes gave the highest disinfection rate that was 46.5%. The modified MS medium included basal MS, 30 g/L sucrose, and 7 g/L agar supplemented with 20 ml/L of coconut water (MS medium*) was the most suitable for the rapid multiplication of Eucalyptus lines U16, the shoot multiplication coefficient reached 1.56. In vitro multiplication of eucalyptus U16 was carried out by culturing disinfected shoot segments on the MS* medium supplemented with BAP 1.5 mg/L and kinetin 1.0 mg/L which gave the highest shoot multiplication coefficient (3.24 shoot per explant). The in vitro rooting medium of the U16 line was basal MS supplemented with 1.0 mg NAA/L, the rooting rate was 90.49%, the number of roots was 8.3, and the roots expressed strong growth

Integrating ATAC-seq and RNA-seq to identify differentially expressed genes with chromatin-accessible changes during photosynthetic establishment in Populus leaves.

Leaves are the primary photosynthetic organs, providing essential substances for tree growth. It is important to obtain an anatomical understanding and regulatory network analysis of leaf development. Here, we studied leaf development in Populus Nanlin895 along a development gradient from the newly emerged leaf from the shoot apex to the sixth leaf (L1 to L6) using anatomical observations and RNA-seq analysis. It indicated that mesophyll cells possess obvious vascular, palisade, and spongy tissue with distinct intercellular spaces after L3. Additionally, vacuoles fuse while epidermal cells expand to form pavement cells. RNA-seq analysis indicated that genes highly expressed in L1 and L2 were related to cell division and differentiation, while those highly expressed in L3 were enriched in photosynthesis. Therefore, we selected L1 and L3 to integrate ATAC-seq and RNA-seq and identified 735 differentially expressed genes (DEGs) with changes in chromatin accessibility regions within their promoters, of which 87 were transcription factors (TFs), such as ABI3VP1, AP-EREBP, MYB, NAC, and GRF. Motif enrichment analysis revealed potential regulatory functions for the DEGs through upstream TFs including TCP, bZIP, HD-ZIP, Dof, BBR-BPC, and MYB. Overall, our research provides a potential molecular foundation for regulatory network exploration in leaf development during photosynthesis establishment.

XAANTAL1 Reveals an Additional Level of Flowering Regulation in the Shoot Apical Meristem in Response to Light and Increased Temperature in Arabidopsis.

Light and photoperiod are environmental signals that regulate flowering transition. In plants like Arabidopsis thaliana, this regulation relies on CONSTANS, a transcription factor that is negatively posttranslational regulated by phytochrome B during the morning, while it is stabilized by PHYA and cryptochromes 1/2 at the end of daylight hours. CO induces the expression of FT, whose protein travels from the leaves to the apical meristem, where it binds to FD to regulate some flowering genes. Although PHYB delays flowering, we show that light and PHYB positively regulate XAANTAL1 and other flowering genes in the shoot apices. Also, the genetic data indicate that XAL1 and FD participate in the same signaling pathway in flowering promotion when plants are grown under a long-day photoperiod at 22 °C. By contrast, XAL1 functions independently of FD or PIF4 to induce flowering at higher temperatures (27 °C), even under long days. Furthermore, XAL1 directly binds to FD, SOC1, LFY, and AP1 promoters. Our findings lead us to propose that light and temperature influence the floral network at the meristem level in a partially independent way of the signaling generated from the leaves.

Integrative Effect of UV-B and Some Organic Amendments on Growth, Phenolic and Flavonoid Compounds, and Antioxidant Activity of Basil (Ocimum basilicum L.) Plants

The application of organic amendments, biochar, and wood distillate (WD), as well as the exposure to UV-B radiation, are two sustainable ways to enhance soil fertility and increase plant nutraceutical quality, respectively. However, they have always been studied separately, without testing the eventual synergistic or antagonistic effect when applied together. The present study investigated the effects of biochar (2% w/w), WD (1:100), and their combination (BWD) on some biometric and biochemical parameters of basil plants (Ocimum basilicum L.) exposed to different doses of UV-B radiation (0, 1, 2 h d−1; UV-B irradiance of 1.36 W m−2) in controlled conditions. Root and stem length and weight were not affected by soil amendments, while 1 h d−1 UV-B increased the length (+28%) and weight (+62%) of the aerial part. When combining the above- and below-ground factors, a decrease in root length was observed in the 2 h d−1 UV-B-treated plants in both WD (−36%) and BWD (−39%) treatments. The co-application of below- and above-ground treatments generally decreased phenolic and flavonoid concentration in both fully expanded leaves and vegetative shoot apices. This preliminary study highlights an antagonistic action of the combination of the investigated factors, at these doses, on the plant growth and metabolism that should be considered.

Morpho-anatomy of in vitro germination and cryopreservation of the orchid Cattleya crispa (Orchidaceae)

Introduction: Cattleya crispa is an ornamental epiphytic orchid with geographic distribution restricted to the Brazilian Atlantic Forest. Due to predatory extractivism and human-induced habitat loss, this species appears on the Red List of Brazilian Flora. Objective: To characterize morpho-anatomical aspects regarding germination and post-seminal development from C. crispa seeds; as well as studying the effect of cryopreservation on these seeds. Methods: We used light microscopy and electron microscopy to describe the microstructure of a 100 ripe seeds. We evaluated seed viability, seed germination, survival rate and protocorm weight in cryopreserved and non-cryopreserved material, with four replicas per treatment using 20 mg of plant material. Results: The seeds are fusiform, whitish yellow with a length from 700 to 900 µm and a water content of 5 %. Germination began seven days after sowing, the formation of the globular protocorm at 30 days and the formation of the seedling occurred 150 days. The persistent seed coat can compress the protocorm and cause it to collapse. The cryopreserved seeds presented 87.15 % viability, 78.32 % germination, 8.48 % survival and protocorms with 104.27 mg five months after sowing. Data wasn’t different to non-cryopreserved seeds. Conclusions: The cryocapability of the seeds shows that cryopreservation can be used for long-term conservation. The results of this work contribute to the overall biology of C. crispa and to the propagation and storage of genetic material for conservation purposes. Objective: To characterize morpho-anatomical aspects regarding germination and initial development from C. crispa seeds; as well as studying the effect of cryopreservation on these seeds. Methods: Mature capsules of C. crispa were collected from the ex-situ conservation collection of the Orquidário Frederico Carlos Hoehne - Institute of Botany (São Paulo-Brazil). We used light microscopy, scanning electron microscopy and transmission electron microscopy. Seed viability (%), seed germination (%), survival rate (%) and protocorms weight (mg) were evaluated. Results: Our analyses showed that the globular embryo has a homogeneously early germination that occurs by the 7th day. The germinating protocorm shows bipolarity, with shoot apex and basal region. The embryo is composed mostly of lipid and protein bodies and contains a few small grains of starch. Scanning electron microscopy images revealed a persistent seed coat that does not influence the onset of germination, however, can compress the protocorm and lead to its collapse. The initial water content of the seeds was 5 %. Seeds submitted to cryopreservation resulted in a high germination rate (81.14 %). However, the survival rate of non-cryopreserved (8.48 %) and cryopreserved (11.12 %) protocorms, evaluated five months after sowing, was reduced. Conclusions: The cryocapability of the seeds shows that cryopreservation can be used for long-term conservation. The results of this work contribute to the overall biology of C. crispa and to the propagation and storage of genetic material for conservation purposes.

Nitric oxide working: no worries about heat stress.

Nitric oxide (NO) has multifaceted roles in plants. He et al. report that NO produced in the shoot apex causes S-nitrosation of transcription factor GT-1. This mediator of NO signal perception subsequently regulates the expression of the HEAT SHOCK TRANSCRIPTION FACTOR A2 (HSFA2) gene, thus leading to thermotolerance in Arabidopsis thaliana.

Apical Dominance and Branching in Plantlets of Colt Cherry Lines Expressing Different Light and Auxin Signalling Sensitivities

The establishment of plant architecture requires coordination of distinct processes including shoot branching and apical dominance (AD). AD involves the bud apical shoot, mainly through indole-3-acetic acid (IAA) synthetized by the cells of the meristem and young leaves. The rootward flow generates an auxin gradient in the stem and buds, regulating lateral bud (LB) outgrowth. Phytochromes and AD are involved in the shade-avoidance syndrome in woody plants. However, the underlying mechanisms remain poorly understood. The aim of this study was to evaluate the sensitivity of cherry rootstocks to light, mediated by the photoreceptor phytochrome, and its effect on the role of auxin in driving branching by AD. Pharmacological treatments using transport inhibitors and a competitor of IAA were applied to transgenic lines of Colt cherry rootstock, which showed different sensitivities to light because of the ectopic expression of a rice phyA gene. Results showed different physiological behaviours among the transgenic lines and between themselves and the Colt-wt line. Exogenous IBA inhibited Colt-wt LB outgrowth, and this inhibition was less intense in transgenic lines. The IAA-inhibitors and IAA-competitor promoted branching. In in vitro phyA-transgenic plantlets, the ectopic gene induced greater branching and a higher number of buds developed in new shoots. This work confirms a positive action of phytochrome on lateral branching in cherry rootstock, playing a role in the regulation of AD. Moreover, we suggest that the confined in vitro system might now be used as a phenotyping screening to test the plasticity of the response, highlighting the behaviour of modified genotypes due to an ectopic insertion event by simple and rapid procedures.

Warm temperature during floral bud transition turns off EjTFL1 gene expression and promotes flowering in Loquat (Eriobotrya japonica Lindl.)

The Rosaceae family includes several deciduous woody species whose flower development extends over two consecutive growing seasons with a winter dormant period in between. Loquat (Eriobotrya japonica Lindl.) belongs to this family, but it is an evergreen species whose flower bud initiation and flowering occur within the same growing year. Vegetative growth dominates from spring to late summer when terminal buds bloom as panicles. Thus, its floral buds do not undergo winter dormancy until flowering, but a summer heat period of dormancy is required for floral bud differentiation, and that is why we used loquat to study the mechanism by which this summer rest period contributes to floral differentiation of Rosaceae species. As for the deciduous species, the bud transition to the generative stage is initiated by the floral integrator genes. There is evidence that combinations of environmental signals and internal cues (plant hormones) control the expression of TFL1, but the mechanism by which this gene regulates its expression in loquat needs to be clarified for a better understanding of its floral initiation and seasonal growth cycles. Under high temperatures (>25ºC) after floral bud inductive period, EjTFL1 expression decreases during meristem transition to the reproductive stage, and the promoters of flowering (EjAP1 and EjLFY) increase, indicating that the floral bud differentiation is affected by high temperatures. Monitoring the apical meristem of loquat in June-August of two consecutive years under ambient and thermal controlled conditions showed that under lower temperatures (<25ºC) during the same period, shoot apex did not stop growing and a higher EjTFL1 expression was recorded, preventing the bud to flower. Likewise, temperature directly affects ABA content in the meristem paralleling EjTFL1 expression, suggesting signaling cascades could converge to refine the expression of EjTFL1 under specific conditions (Tª<25ºC) during the floral transition stage.

Self-grafting induced epigenetic changes leading to drought stress tolerance in tomato plants.

Grafting is widely used as a method to increase stress tolerance in good fruiting lines of Solanaceae plants. However, little is known about how grafting, affects epigenetic modifications and leads to stress tolerance, especially within the same line. Here, we studied the effects of self-grafting in tomato plants on histone and DNA modifications and changes in gene expression related to drought stress. We found that at the 3-leaf stage, one week after self-grafting, histone H3 K4 trimethylation and K27 trimethylation changes were observed in more than 500 genes each, and DNA methylation changes in more than 5,000 gene regions at the shoot apex compared to the non-grafted control. In addition, two weeks after the epigenomic changes, global expression changes continued to be observed at the shoot apex in several genes related to the metabolic process of nitrogen compounds, responses to stimulus, chromosome organization, cell cycle-related genes, and regulation of hormone levels. Finally, these grafted seedlings acquired remarkable drought tolerance, suggesting that epigenomic modifications during the wound-healing process mitigate stress tolerance in tomato plants.

Vine Performance and Phenology Postponement in Cane-Pruned Chardonnay Vines Grown in a Temperate Climate: The Effects of a Delayed Winter Pruning

In a global warming context, the advancement and compression of maturity in early ripening grape varieties suited to sparkling wine making can easily expedite harvest within the first two weeks of August (in northern Italy). Such earliness, albeit safeguarding acid retention, involves potential suboptimal grape composition and triggers logistical issues related to grape harvest and delivery. Hence, this three-year study beginning in 2020 was conducted on cane-pruned Chardonnay vines, grown in the Franciacorta district of Lombardy, to assess if a single-step delayed winter pruning was able to postpone vine phenology and ripening, without harming yield potential. Control (C) vines pruned midwinter were compared with those subjected to late winter pruning (LWP), performed when the apical shoots growing on the unpruned canes had reached the 2-3 unfolded leaf stage (T1) as well as 7-8 days later (T2). In 2022, a fourth treatment was added, consisting of a two-step procedure with finishing performed at T1 (LWP-two canes). Vegetative growth, yield components, ripening dynamics, and maturity at harvest were followed in each year of this study. Budburst delay induced by LWP treatments across seasons varied between 4 and 9 days, whereas harvest was postponed by 5–14 days. The extent of delay was especially pronounced in 2020, when the removed leaf area (LA) was also found to be the highest. The higher the removed LA, the higher the yield constrain was in the concomitant year. In 2020 and 2021, despite the harvest delay, LWP vines were able to assure full matching with desirable features in must composition, set at total soluble solids (TSS) of about 18°Brix and a titratable acidity (TA) of at least 8 g/L. In the very hot and dry phase of 2022, none of the treatments facilitated the required ripening status, while data showed that an even earlier ripening would not have allowed the harvest to reach the minimum TSS level. Notably, even in 2021 and 2022, when the removed LA was quite low, a delaying effect was prompted in the seasonal trends of all main ripening parameters. This suggested that besides the amount of LA removal, other unknown factors drive the postponement of ripening. In 2022, the behavior of added-treatment LWP-two canes was found to be quite similar to that of the C vines. Depending upon the desired yield level and local climate feature, the protocol entailing a single-step late winter pruning, performed at any time between the T1-T2 time window used in this study, is deemed as effective in achieving a significant harvest delay while maintaining or even improving the compositional patterns recorded for midwinter pruned vines.

Genetic and molecular regulation of increased photosynthetic cell number contributes to leaf size heterosis in Arabidopsis

Heterosis is an important genetic phenomenon that has been observed and widely utilized in agriculture. However, the genetic and molecular bases of heterosis are unclear. Through transcriptome-wide association studies (TWAS) and expression quantitative trait locus (eQTL) analysis to integrate genome, transcriptome, and heterotic phenotype of a half-sibling Arabidopsis hybrid population, we report that the genetic and molecular bases of variations in leaf growth heterosis can be explained by the varied expression levels of growth-regulating genes resulting from distinct sets of heterozygous eQTLs carried by the half-sibling hybrids. In F1 versus parent, the degree of up-regulated gene expression in the cell cycle pathway in the shoot apex and the photosynthesis pathway in true leaf positively correlates with true leaf area heterosis level, and this is affected by the accumulation of superior heterozygous eQTLs. This was further corroborated by the major contribution of increased photosynthetic cell number to leaf area heterosis.

Is Twelve Hours Really the Optimum Photoperiod for Promoting Flowering in Indoor-Grown Cultivars of Cannabis sativa?

Cannabis sativa ("cannabis" hereafter) is a valuable recent addition to Canada's economy with the legalization for recreational use in 2018. The vast majority of indoor cannabis cultivators use a 12-h light/12-h dark photoperiod to promote flowering. To test the hypothesis that robust flowering initiation responses can be promoted in indoor-grown cannabis cultivars under longer photoperiods, clones of ten drug-type cannabis cultivars were grown under six photoperiod treatments. All treatments were based on a standard 24-h day and included 12 h, 12.5 h, 13 h, 13.5 h, 14 h, and 15 h of light. The plants were grown in a growth chamber for 3 to 4 weeks, receiving an approximate light intensity of 360 µmol·m-2·s-1 from white LEDs. Flowering initiation, defined as the appearance of ≥3 pairs of stigmas at the apex of the primary shoot, occurred in all cultivars under all photoperiod treatments up to 14 h. Delays in flowering initiation time under 14 h vs. 12 h ranged from no delay to approximately 4 days, depending on the cultivar. Some cultivars also initiated flowering under 15 h, but floral tissues did not further develop beyond the initiation phase. Harvest metrics of some cultivars responded quadratically with increasing photoperiod, with ideal levels of key flowering parameters varying between 12 h and 13 h. These results suggest there is potential to increase yield in some indoor-grown cannabis cultivars by using longer than 12-h photoperiods during the flowering stage of production. This is attributed to the inherently higher daily light integrals. Indoor cannabis growers should investigate the photoperiod responses of their individual cultivars to determine the optimal photoperiod for producing floral biomass.

Mapping and candidate gene analysis of clustered bud on the main inflorescence in Brassica napus L.

Breeding rapeseed varieties with more main inflorescence siliques is an idea for developing rapeseed varieties that are suitable for light and simplified cultivation. The Brassica napus exhibited cluster bud of the main inflorescence (Bnclib) gene. At the fruiting stage, the main inflorescence had more siliques, higher density, and more main inflorescences. Moreover, the top of the main inflorescence bifurcated. Genetic analysis showed that the separation ratio between Bnclib and the wild type in the F2 generation was 3:1, which indicated that the trait was a single-gene-dominant inheritance. Among the 24 candidate genes, only one gene, BnaA03g53930D, showed differential expression between the groups (False discovery rate, FDR ≤ 0.05, |log2FC|≤ 1). qPCR verification of the BnaA03g53930D gene between Huyou 17 and its Bnclib near-isogenic line showed that BnaA03g53930D was significantly differentially expressed in the stem tissue of Huyou 17 and its Bnclib near-isogenic line (Bnclib NIL). The determination of gibberellin (GA), brassinolide (BR), cytokinin (CTK), jasmonic acid (JA), growth hormone (IAA), and strigolactone (SL) content in the shoot apex of Huyou 17 by Bnclib NIL and wild type showed that all six hormones significantly differed between the Bnclib NIL and Huyou 17. It is necessary to conduct further research on the interactions between JA and the other five hormones and the main inflorescence bud clustering in B. napus.

Transcriptome features of stone cell development in weevil-resistant and susceptible Sitka spruce.

Stone cells are a specialized, highly lignified cell type found in both angiosperms and gymnosperms. In conifers, abundance of stone cells in the cortex provides a robust constitutive physical defense against stem feeding insects. Stone cells are a major insect-resistance trait in Sitka spruce (Picea sitchensis), occurring in dense clusters in apical shoots of trees resistant (R) to spruce weevil (Pissodes strobi) but being rare in susceptible (S) trees. To learn more about molecular mechanisms of stone cell formation in conifers, we used laser microdissection and RNA sequencing to develop cell-type-specific transcriptomes of developing stone cells from R and S trees. Using light, immunohistochemical, and fluorescence microscopy, we also visualized the deposition of cellulose, xylan, and lignin associated with stone cell development. A total of 1293 genes were differentially expressed at higher levels in developing stone cells relative to cortical parenchyma. Genes with potential roles in stone cell secondary cell wall formation (SCW) were identified and their expression evaluated over a time course of stone cell formation in R and S trees. The expression of several transcriptional regulators was associated with stone cell formation, including a NAC family transcription factor and several genes annotated as MYB transcription factors with known roles in SCW formation.

IDENTIFICATION AND CHARACTERIZATION OF CASSAVA MUTANT GENOTYPES WITH HIGH LEAF MINERAL CONTENT AT THE MV10 GENERATION

Cassava leaves’ consumption as vegetables are common in several Asian countries. They contain various nutrients, such as, anthocyanins, carotene, minerals, and vitamins. New varieties with high mineral contents in leaves need development to increase the leaves’ quality as vegetables. This study aimed to identify and characterize cassava genotypes of the MV10 generation resulting from gammaray- induced mutations based on the leaves' morphology, growth characteristics, and mineral contents, using two cultivars and 10 cassava genotypes. All genotypes planted in a randomized complete block design had three replications. The leaf's morphology and mineral contents underwent scrutiny on the third to fifth leaf below the apical shoot. The mineral content analysis used the Atomic Absorption Spectrophotometry method. Data analysis comprised the ANOVA test and descriptive analysis. This study revealed petiole length, leaf lobe length, and leaf lobe width were significantly different between genotypes at four months after planting (MAP). However, no meaningful difference showed for the plant height, stem diameter, and number of leaves among genotypes. In general, the leaf morphology consisted of purplish green apical leaves with present pubescence; the shape of the central leaflet is lanceolate; the petiole color is reddish to greenish; leaves are dark green with five to seven leaf lobes; leaf veins are reddish-green; smooth lobe margins; and horizontal petiole orientation. The genotypes affect mineral contents, as the genotype with the highest Mg contents was G6-2-15-5-3, and the one with the highest Zn contents was G2D1-422. Fe contents showed more variations between genotypes, and no genotype showed consistently high Fe contents. This research produced promising genotypes for Mg or Zn contents in leaves for future cassava varieties for vegetable production.

Understanding Transcription Factors and How They Affect Processes in Cucumber Sex Determination.

Plant reproduction is a fundamental process on Earth from the perspective of biodiversity, biomass gain, and crop productivity. It is therefore important to understand the sex determination process, and many researchers are investigating the molecular basis of this phenomenon. However, information on the influence of transcription factors (TFs), genes that encode DNA-binding proteins, on this process is limited, although cucumber is a model plant in this regard. In the present study, based on RNA-seq data for differentially expressed genes (DEGs), we aimed to investigate the regulatory TFs that may influence the metabolic processes in the shoot apex containing the forming flower buds. Therefore, the annotation of the genome of the B10 cucumber line was supplemented with the assigned families of transcription factors. By performing ontology analyses of the DEGs, the processes they participate in were identified, and TFs were located among the results. In addition, TFs that have significantly overrepresented targets among DEGs were detected, and sex-specific interactome network maps were generated, indicating the regulatory TFs based on their effects on DEGs and furthermore, on the processes leading to the formation of different-sex flowers. Among the most overrepresented TF families in the sex comparisons were the NAC, bHLH, MYB, and bZIP families. An interaction network analysis indicated the most abundant families among DEGs' regulatory TFs were MYB, AP2/ERF, NAC, and bZIP, and those with the most significant impact on developmental processes were identified, namely the AP/ERF family, followed by DOF, MYB, MADS, and others. Thus, the networks' central nodes and key regulators were identified with respect to male, female, and hermaphrodite forms. Here, we proposed the first model of the regulatory network of TFs that influences the metabolism of sex development in cucumber. These findings may help us to understand the molecular genetics and functional mechanisms underlying sex determination processes.