Leaf Color Variation Research Articles

Anthocyanin Biosynthesis Associated with Natural Variation in Autumn Leaf Coloration in Quercus aliena Accessions.

Quercus aliena is an economically important tree species and one of the dominant native oak species in China. Although its leaves typically turn yellow in autumn, we observed natural variants with red leaves. It is important to understand the mechanisms involved in leaf color variation in this species. Therefore, we compared a Q. aliena tree with yellow leaves and three variants with red leaves at different stages of senescence in order to determine the causes of natural variation. We found that the accumulation of anthocyanins such as cyanidin 3-O-glucoside and cyanidin 3-O-sambubiglycoside had a significant effect on leaf coloration. Gene expression analysis showed upregulation of almost all genes encoding enzymes involved in anthocyanin synthesis in the red-leaved variants during the early and main discoloration stages of senescence. These findings are consistent with the accumulation of anthocyanin in red variants. Furthermore, the variants showed significantly higher expression of transcription factors associated with anthocyanin synthesis, such as those encoded by genes QaMYB1 and QaMYB3. Our findings provide new insights into the physiological and molecular mechanisms involved in autumn leaf coloration in Q. aliena, as well as provide genetic resources for further development and cultivation of valuable ornamental variants of this species.

Comprehensive Comparison of Two Color Varieties of Perillae Folium by GC-MS-Based Metabolomic Approach.

Perillae Folium (PF), the leaf of Perilla frutescens (L.) Britt, is extensively used as culinary vegetable in many countries. It can be divided into two major varietal forms based on leaf color variation, including purple PF (Perilla frutescens var. arguta) and green PF (P. frutescens var. frutescens). The aroma of purple and green PF is discrepant. To figure out the divergence of chemical composition in purple and green PF, gas chromatography–tandem mass spectrometry (GC-MS) was applied to analyze compounds in purple and green PF. A total of 54 compounds were identified and relatively quantified. Multivariate statistical methods, including principal component analysis (PCA), orthogonal partial least-squares discrimination analysis (OPLS-DA) and clustering analysis (CA), were used to screen the chemical markers for discrimination of purple and green PF. Seven compounds that accumulated discrepantly in green and purple PF were characterized as chemical markers for the discrimination of the purple and green PF. Among these 7 marker compounds, limonene, shisool and perillaldehyde that from the same branch of the terpenoid biosynthetic pathway were with relatively higher contents in purple PF, while perilla ketone, isoegomaketone, tocopheryl and squalene on other branch pathways were higher in green PF. The results of the present study are expected to provide theoretical support for the development and utilization of PF resources.

Transcriptomic Analysis of the Differences in Leaf Color Formation during Stage Transitions in Populus × euramericana ‘Zhonghuahongye’

To explore the mechanism underlying the leaf color variation of Populus × euramericana ‘Zhonghuahongye’ (‘Zhonghong’ poplar) leaves at different maturation stages, we used ‘Zhonghong’ poplar leaves and analyzed the L* (lightness), a* (redness), and b* (yellowness) color difference values and the pigment contents in the three maturation stages. The Illumina HiSeqTM 2000 high−throughput sequencing platform was used for transcriptome sequencing analysis, and leaf color changes during stage transitions were preliminarily explored. Overall, with the increase in L* and b* during leaf development, the a*, C* (colour saturation), and chromatic values decreased, the total anthocyanin content decreased, and the chlorophyll and carotenoid content increased. A total of 11,868 differentially expressed genes were identified by transcriptome sequencing. Comparing the expression differences of structural genes involved in anthocyanin synthesis in the leaves at different stages, we identified 5612 genes in the R1 vs. R2 comparison, 10,083 in the R1 vs. R3 comparison, and 6068 in the R2 vs. R3 comparison (R1, R2, R3 refer to samples obtained on 1 April, 6 April, and 11 April, respectively). Key genes such as DFR (Dihydroflavanol 4−reductase), ANS (anthocyanidin synthase), FLS(flavonol synthase) , CHS(chalcone synthase), BZ1(Bronze 1), bHLH35, and bHLH63 were identified. These structural genes and those that encode transcription factors may be related to the regulation of anthocyanin synthesis. Here, the key genes related to leaf color change in ‘Zhonghong’ poplar were discovered, providing an important genetic basis for the subsequent genetic improvement of ‘Zhonghong’ poplar.

Translational landscape and metabolic characteristics of the etiolated tea plant (Camellia sinensis)

• Transcriptome, translatome, and metabolome were used to analyse tea etiolation. • Ribosome profiling reveals carbon and phytohormone metabolism mediate leaf etiolation. • HY5 inhibited chlorophyll and flavonoids metabolism in etiolated leaf. • Changes in gene structure between EL and GL influence their gene expression. Albino tea plants ( Camellia sinensis , Atps) are among the most attractive germplasm resources because of their unique phenotype and flavor. Although previous studies have extensively investigated the transcriptional and metabolic mechanisms in Atps, the lack of research at the translational level hinders the understanding of translation control and multi-omics integration. Here, we integrated the transcriptome, translatome, and metabolome to study the global translation and its effect on the metabolic characteristics of Atps. Comparative analysis of RNA-seq and Ribo-seq datasets indicated that 4,295 genes were expressed as synergic responses in etiolated leaves and were mainly enriched in the carbon metabolism and phytohormone pathways. Further integration-omics analyses revealed that the HY5 gene was upregulated at both the transcription and translation levels and repressed chlorophyll biosynthesis and flavonoids metabolism due to low levels of indole acetic acid and auxin response factors. Moreover, sequence characterizations (guanine-cytosine (GC) content, length, and normalized minimal free energy (NMFE)) highly influenced the translational efficiencies (TE) of genes and upstream open reading frames (uORFs), and a higher quantity of uORFs and TE were observed in EL, inhibiting the expression of downstream genes. In summary, we demonstrated that translation regulation contributes to causing leaf color variation and provided a valuable method for exploring the potential regulatory mechanisms controlling phytohormones that affect crop quality using multi-omics technology.

Metabolome and Transcriptome Analyses Unravels Molecular Mechanisms of Leaf Color Variation by Anthocyanidin Biosynthesis in Acer triflorum

Acer triflorum Komarov is an important ornamental tree, and its seasonal change in leaf color is the most striking feature. However, the quantifications of anthocyanin and the mechanisms of leaf color change in this species remain unknown. Here, the combined analysis of metabolome and transcriptome was performed on green, orange, and red leaves. In total, 27 anthocyanin metabolites were detected and cyanidin 3-O-arabinoside, pelargonidin 3-O-glucoside, and peonidin 3-O-gluside were significantly correlated with the color development. Several structural genes in the anthocyanin biosynthesis process, such as chalcone synthase (CHS), flavanone 3-hydroxylase (F3H), and dihydroflavonol 4-reductase (DFR), were highly expressed in red leaves compared to green leaves. Most regulators (MYB, bHLH, and other classes of transcription factors) were also upregulated in red and orange leaves. In addition, 14 AtrMYBs including AtrMYB68, AtrMYB74, and AtrMYB35 showed strong interactions with the genes involved in anthocyanin biosynthesis, and, thus, could be further considered the hub regulators. The findings will facilitate genetic modification or selection for further improvement in ornamental qualities of A. triflorum.

Cytological, Biochemical, and Transcriptomic Analyses of a Novel Yellow Leaf Variation in a Paphiopedilum (Orchidaceae) SCBG COP15.

The genus Paphiopedilum, belonging to the Orchidaceae, has high ornamental value. Leaf variations can considerably improve the economic and horticultural value of the orchids. In the study, a yellow leaf mutant of a Paphiopedilum hybrid named P. SCBG COP15 was identified during the in vitro plant culture process; however, little is known about their molecular mechanisms. For this, RNA-seq libraries were created and used for the transcriptomic profiling of P. SCBG COP15 and the yellow mutant. The Chl a, Chl b, and carotenoid contents in the yellow leaves decreased by approximately 75.99%, 76.92%, and 56.83%, respectively, relative to the green leaves. Decreased chloroplasts per cell and abnormal chloroplast ultrastructure were observed by electron microscopic investigation in yellowing leaves; photosynthetic characteristics and Chl fluorescence parameters were also decreased in the mutant. Altogether, 34,492 unigenes were annotated by BLASTX; 1,835 DEGs were identified, consisting of 697 upregulated and 1138 downregulated DEGs. HEMA, CRD, CAO, and CHLE, involved in Chl biosynthesis, were predicted to be key genes responsible for leaf yellow coloration. Our findings provide an essential genetic resource for understanding the molecular mechanism of leaf color variation and breeding new varieties of Paphiopedilum with increased horticultural value.

Investigating the Rainforest Canopy Phenology Variation and Productivity Responses to Drought by Using Digital Camera Images

Among the natural disturbances, drought may cause significant change in forest ecosystems by shifting phenology and productivity. Digital cameras have been used in phenological observations for their high accuracy and the colour index values (digital-number of red, green and blue) derived from long-term continuous digital camera imagery are useful as proxies for investigating a forest canopy’s response to drought. Here, we examine the interaction between colour indices (the strength of red (Sred), the strength of green (Sgreen), green excess index (GEI)), productivity (gross primary productivity (GPP)) and drought (standardised precipitation evapotranspiration index (SPEI)) and climatic factors. We use forest canopy images derived from a digital camera and flux tower-based productivity from 2010 to 2016 to show the rainforest’s responses to drought in phenology and productivity. The SPEI indicated the occurrence of drought condition in 2014. The lowest values of the SPEI (-0.403 mmday-1), and total precipitation (1062 mmyr-1), and the highest values of average air temperature (21.3 C)”, need to be changed like that “the highest values of average air temperature (21.3°C)”, to put Degree symbol between the 21.3 and C, potential evapotranspiration (3.31 mmday-1) and rain use efficiency (2.26 gCL-1) were found in 2014. Leaf color variation period (CVP) become longer with an advance in foliage green-up after drought. The peak GEI values were found at the end of the CVPs. The GPP and the Sgreen had positive and the Sred had negative relationship with drought index. The GPP dropped during the drought and bounced back after the drought due to a longer leaf CVP. The Sgreen and GEI were significantly (p<0.05) related to GPP during the drought. During the CVP of the drought, the Sgreen and GEI were significantly correlated (p<0.05) with total P, PET and average Ta, meanwhile, there was only a significant relationship (p<0.05) between the GPP with PET and avg Ta. Among the variables, the GPP was more significant (p < 0.001) with avg Ta. There was also a relationship between the colour indices and GPP with climatic factors on a yearly time series. Our results indicate an understanding of the phenology and productivity response of rainforests to drought, which might be useful for ecologists when predicting the effects of future climatic change on rainforest phenology and productivity.

Comparative transcriptome and microbial community sequencing provide insight into yellow-leaf phenotype of Camellia japonica

BackgroundLeaf color variation is a common trait in plants and widely distributed in many plants. In this study, a leaf color mutation in Camellia japonica (cultivar named as Maguxianzi, M) was used as material, and the mechanism of leaf color variation was revealed by physiological, cytological, transcriptome and microbiome analyses.ResultsThe yellowing C. japonica (M) exhibits lower pigment content than its parent (cultivar named as Huafurong, H), especially chlorophyll (Chl) and carotenoid, and leaves of M have weaker photosynthesis. Subsequently, the results of transmission electron microscopy(TEM) exhibited that M chloroplast was accompanied by broken thylakoid membrane, degraded thylakoid grana, and filled with many vesicles. Furthermore, comparative transcriptome sequencing identified 3,298 differentially expressed genes (DEGs). KEGG annotation analysis results showed that 69 significantly enriched DEGs were involved in Chl biosynthesis, carotenoid biosynthesis, photosynthesis, and plant-pathogen interaction. On this basis, we sequenced the microbial diversity of the H and M leaves. The sequencing results suggested that the abundance of Didymella in the M leaves was significantly higher than that in the H leaves, which meant that M leaves might be infected by Didymella.ConclusionsTherefore, we speculated that Didymella infected M leaves while reduced Chl and carotenoid content by damaging chloroplast structures, and altered the intensity of photosynthesis, thereby causing the leaf yellowing phenomenon of C. japonica (M). This research will provide new insights into the leaf color variation mechanism and lay a theoretical foundation for plant breeding and molecular markers.

Mapping of a Pale Green Mutant Gene and Its Functional Verification by Allelic Mutations in Chinese Cabbage (Brassica rapa L. ssp. pekinensis).

Leaves are the main organ for photosynthesis, and variations in leaf color affect photosynthesis and plant biomass formation. We created two similar whole-plant pale green mutants (pem1 and pem2) from the double haploid (DH) Chinese cabbage line “FT” through ethyl methanesulfonate (EMS) mutagenesis of seeds. Photosynthetic pigment contents and net photosynthetic rates were significantly lower in the mutants than in the wild-type “FT,” and the chloroplast thylakoid endomembrane system was poor. Genetic analysis showed that the mutated phenotypes of pem1 and pem2 were caused by a single nuclear gene. Allelism tests showed that pem1 and pem2 were alleles. We mapped Brpem1 to a 64.25 kb region on chromosome A10, using BSR-Seq and map-based cloning of 979 F2 recessive individuals. Whole-genome re-sequencing revealed a single nucleotide polymorphism (SNP) transition from guanine to adenosine on BraA10g021490.3C in pem1, causing an amino acid shift from glycine to glutamic acid (G to E); in addition, BraA10g021490.3C in pem2 was found to have a single nucleotide substitution from guanine to adenosine, causing an amino acid change from E to lysine (K). BraA10g021490.3C is a homolog of the Arabidopsisdivinyl chlorophyllide a 8-vinyl-reductase (DVR) gene that encodes 3,8-divinyl protochlorophyllide a 8-vinyl reductase, which is a key enzyme in chlorophyll biosynthesis. Enzyme activity assay and chlorophyll composition analysis demonstrated that impaired DVR had partial loss of function. These results provide a basis to understand chlorophyll metabolism and explore the mechanism of a pale green phenotype in Chinese cabbage.

Frequent gain- and loss-of-function mutations of the BjMYB113 gene accounted for leaf color variation in Brassica juncea

BackgroundMustard (Brassica juncea) is an important economic vegetable, and some cultivars have purple leaves and accumulate more anthocyanins than the green. The genetic and evolution of purple trait in mustard has not been well studied.ResultIn this study, free-hand sections and metabolomics showed that the purple leaves of mustard accumulated more anthocyanins than green ones. The gene controlling purple leaves in mustard, Mustard Purple Leaves (MPL), was genetically mapped and a MYB113-like homolog was identified as the candidate gene. We identified three alleles of the MYB113-like gene, BjMYB113a from a purple cultivar, BjMYB113b and BjMYB113c from green cultivars. A total of 45 single nucleotide polymorphisms (SNPs) and 8 InDels were found between the promoter sequences of the purple allele BjMYB113a and the green allele BjMYB113b. On the other hand, the only sequence variation between the purple allele BjMYB113a and the green allele BjMYB113c is an insertion of 1,033-bp fragment in the 3’region of BjMYB113c. Transgenic assay and promoter activity studies showed that the polymorphism in the promoter region was responsible for the up-regulation of the purple allele BjMYB113a and high accumulation of anthocyanin in the purple cultivar. The up-regulation of BjMYB113a increased the expression of genes in the anthocyanin biosynthesis pathway including BjCHS, BjF3H, BjF3’H, BjDFR, BjANS and BjUGFT, and consequently led to high accumulation of anthocyanin. However, the up-regulation of BjMYB113 was compromised by the insertion of 1,033-bp in 3’region of the allele BjMYB113c.ConclusionsOur results contribute to a better understanding of the genetics and evolution of the BjMYB113 gene controlling purple leaves and provide useful information for further breeding programs of mustard.

Characterization of Indian spinach (Basella spp.) genotypes under Chhattisgarh plain conditions

Germplam characterization was centered primarily on two major species, Basella alba L. and Basella rubra L. of the twenty four under study, Chadra, Bombay White, Soda Mota Pui, IGPB-2017-01, IGPB-2017-02, IGPB-2017-03, IGPB-2017-04, IGPB-2017-05, IGPB-2017-06, IGPB-2017-07, IGPB-2017-08, IGPB-2017-09, white green leaf margin colour were recognized as Basella alba L., while IGPB-2017-10, IGPB-2017-11, IGPB-2017-12, IGPB-2017-13, IGPB-2017-14, IGPB-2017-15, IGPB-2017-16, IGPB-2017-17, IGPB-2017-18, IGPB-2017-19, IGPB-2017-20, IGPB-2017-21 with red leaf margin colour was recognized as Basella rubra L. Germaplam characterization was centered secondarily on quantitative traits. Twenty four landraces of Indian spinach characterized in this study showed a broad variation for most of the qualitative traits under study. The variation in leaf colour, leaf shape, stem colour, stem shape, leaf margin colour, leaf margin and flower colour, were easily recognizable with visual appraisal in the material.

Metabolomic and transcriptomic analyses of mutant yellow leaves provide insights into pigment synthesis and metabolism in Ginkgo biloba

BackgroundGinkgo (Ginkgo biloba L.) is an excellent landscape species. Its yellow-green leaf mutants are ideal materials for research on pigment synthesis, but the regulatory mechanism of leaf coloration in these ginkgo mutants remains unclear.ResultsWe compared the metabolomes and transcriptomes of green and mutant yellow leaves of ginkgo over the same period in this study. The results showed that the chlorophyll content of normal green leaves was significantly higher than that of mutant yellow leaves of ginkgo. We obtained 931.52M clean reads from different color leaves of ginkgo. A total of 283 substances in the metabolic profiles were finally detected, including 50 significantly differentially expressed metabolites (DEMs). We identified these DEMs and 1361 differentially expressed genes (DEGs), with 37, 4, 3 and 13 DEGs involved in the photosynthesis, chlorophyll, carotenoid, and flavonoid biosynthesis pathways, respectively. Moreover, integrative analysis of the metabolomes and transcriptomes revealed that the flavonoid pathway contained the upregulated DEM (−)-epicatechin. Fourteen DEGs from the photosynthesis pathway were positively or negatively correlated with the DEMs.ConclusionsOur findings suggest a complex metabolic network in mutant yellow leaves. This study will provide a basis for studies of leaf color variation and regulation.

Label-free comparative proteomic and physiological analysis provides insight into leaf color variation of the golden-yellow leaf mutant of Lagerstroemia indica

GL1 is a golden-yellow leaf mutant that cultivated from natural bud-mutation of Lagerstroemia indica and has a very low level of photosynthetic pigment under sunlight. GL1 can gradually increase its pigment content and turn into pale-green leaf when shading under sunshade net (referred as Re-GL1). The mechanisms that cause leaf color variation are complicated and are not still unclear. Here, we have used a label-free comparative proteomics to investigate differences in proteins abundance and analyze the specific biological process associated with mechanisms of leaf color variation in GL1. A total of 245 and 160 proteins with different abundance were identified in GL1 vs WT and GL1 vs Re-GL1, respectively. Functional classification analysis revealed that the proteins with different abundance mainly related to photosynthesis, heat shock proteins, ribosome proteins, and oxidation-reduction. The proteins that the most significantly contributed to leaf color variation were photosynthetic proteins of PSII and PSI, which directly related to photooxidation and determined the photosynthetic performance of photosystem. Further analysis demonstrated that low jasmonic acid content was needed to golden-yellow leaf GL1. These findings lay a solid foundation for future studies into the molecular mechanisms that underlie leaf color formation of GL1. Biological significanceThe natural bud mutant GL1 of L. indica is an example through changing leaf color to cope with complex environment. However, the molecular mechanism of leaf color variation are largely elusive. The proteins with different abundance identified from a label-free comparative proteomics revealed a range of biological processes associated with leaf color variation, including photosynthesis, oxidation-reduction and jasmonic acid signaling. The photooxidation and low level of jasmonic acid played a primary role in GL1 adaptation in golden-yellow leaf. These findings provide possible pathway or signal for the molecular mechanism associated with leaf color formation and as a valuable resource for signal transaction of chloroplast.

Repressed Gene Expression of Photosynthetic Antenna Proteins Associated with Yellow Leaf Variation as Revealed by Bulked Segregant RNA-seq in Tea Plant Camellia sinensis.

The young leaves and shoots of albino tea cultivars are usually characterized as having a yellow or pale color, high amino acid, and low catechin. Increasing attention has been paid to albino tea cultivars in recent years because their tea generally shows high umami and reduced astringency. However, the genetic mechanism of yellow-leaf variation in albino tea cultivar has not been elucidated clearly. In this study, bulked segregant RNA-seq (BSR-seq) was performed on bulked yellow- and green-leaf hybrid progenies from a leaf color variation population. A total of 359 and 1134 differentially expressed genes (DEGs) were identified in the yellow and green hybrid bulked groups (Yf vs Gf) and parent plants (Yp vs Gp), respectively. The significantly smaller number of DEGs in Yf versus Gf than in Yp versus Gp indicated that individual differences could be reduced within the same hybrid progeny. Analysis of Gene Ontology and Kyoto Encyclopedia of Genes and Genomes revealed that the photosynthetic antenna protein was most significantly enriched in either the bulked groups or their parents. Interaction was found among light-harvesting chlorophyll a/b -binding proteins (LHC), heat shock proteins (HSPs), and enzymes involved in cuticle formation. Combined with the transcriptomic expression profile, results showed that the repressed genes encoding LHC were closely linked to aberrant chloroplast development in yellow-leaf tea plants. Furthermore, the photoprotection and light stress response possessed by genes involved in HSP protein interaction and cuticle formation were discussed. The expression profile of DEGs was verified via quantitative real-time PCR analysis of the bulked samples and other F1 individuals. In summary, using BSR-seq on a hybrid population eliminated certain disturbing effects of genetic background and individual discrepancy, thereby helping this study to intensively focus on the key genes controlling leaf color variation in yellow-leaf tea plants.

The source material for the selection of decorative sunflower

Seven lines of analogs with different color of leaves were created in sunflower by the backcross method of the recipient line of YuV-28B and gene donors controlling different variations in leaf color. A study of these lines at the Research Institute of Agriculture of the South-East region in 2017–2019, conducted as a competitive variety test, showed that most seed lines did not significantly differ in seed yield from the recipient line YuV-28B except for the L-4 line with olive color of the sheet, in which this indicator was lower than that of the recipient line. They were assessed analogous lines according to the phenological, morphological, crop-forming characteristics, as well as according to the quality of seeds and oil. All analogue lines had 100% shell of seeds and resistance to local races of broomrape and downy mildew. Most of the studied indicators of these lines correspond to the parameters of the source material, so they can be used in the selection of decorative sunflower.

Development and Characterization of an Ethyl Methane Sulfonate (EMS) Induced Mutant Population in Capsicum annuum L.

Plant breeding explores genetic diversity in useful traits to develop new, high-yielding, and improved cultivars. Ethyl methane sulfonate (EMS) is a chemical widely used to induce mutations at loci that regulate economically essential traits. Additionally, it can knock out genes, facilitating efforts to elucidate gene functions through the analysis of mutant phenotypes. Here, we developed a mutant population using the small and pungent ornamental Capsicum annuum pepper “Micro-Pep”. This accession is particularly suitable for mutation studies and molecular research due to its compact growth habit and small size. We treated 9500 seeds with 1.3% EMS and harvested 3996 M2 lines. We then selected 1300 (32.5%) independent M2 families and evaluated their phenotypes over four years. The mutants displayed phenotypic variations in plant growth, habit, leaf color and shape, and flower and fruit morphology. An experiment to optimize Targeting Induced Local Lesions IN Genomes (TILLING) in pepper detected nine EMS-induced mutations in the eIF4E gene. The M2 families developed here exhibited broad phenotypic variation and should be valuable genetic resources for functional gene analysis in pepper molecular breeding programs using reverse genetics tools, including TILLING.

Color characteristics, pigment accumulation and biosynthetic analyses of leaf color variation in herbaceous peony (Paeonia lactiflora Pall.).

Herbaceous peony (Paeonia lactiflora Pall.) is one of the color-leaved ornamental spring plants, with graceful appearance and splendid color. However, the underlying mechanism of this coloration variation from purple to green has not been studied in P. lactiflora. In th study, the leaves in purple, purple-green, and green stages were compared in terms of anatomical, physiological, and molecular. We found that the variation of leaf color from purple to green was mainly determined by the change in pigments distributed in the leaf surface. Physiological experiments showed a significant increase in chlorophyll contents and a notable reduction in anthocyanin contents in leaves from the purple to green stages. We further found that the anthocyanin biosynthesis-related dihydroflavonol 4-reductase (DFR) gene and anthocyanin synthase (ANS) gene as well as chlorophyll biosynthesis-related glutamyl-tRNA reductase (HEMA) gene showed a decreased trend in leaves from purple to green stages, whereas the chlorophyll degradation-related chlorophyll b reductase (NYC) gene showed a rising trend. Alteration of DFR and ANS gene expression might reduce anthocyanin accumulation, whereas increased HEMA gene expression would enhance chlorophyll biosynthesis and reduced NYC gene expression would inhibit chlorophyll degradation. Consequently, reduction in anthocyanins and enhanced deposition of chlorophylls resulted in leaf coloration variation from purple to green in P. lactiflora, which could improve our understanding of its mechanism for further studies.

Pale green mutant analyses reveal the importance of CsGLKs in chloroplast developmental regulation and their effects on flavonoid biosynthesis in tea plant

Tea cultivars with leaf color variation have attracted increasing attention in tea production and research due to their unusual appearances and appealing flavors. However, the molecular mechanism underlying this variation is little known due to the unavailability of genetic transformation and a highly complex genome. Here, a natural tea plant mutant producing pale green branches (pgb) was discovered and characterized. Ultrastructural and biochemical analyses showed that the leaves of the pgb mutant had defective chloroplast structure and significantly lower pigment content than the normal control. Comprehensive expression detection of chloroplast-development-related genes further indicated that a significant downregulation of CsGLKs in the pgb mutant likely caused the chloroplast defect. Transcriptome analyses and polyphenolic compound determination highlighted a tight correlation between photosynthesis and secondary metabolite biosynthesis in tea plant. These results provide useful information illuminating the mechanism of chloroplast development and leaf color variation in tea plant.

Physiological and transcriptomic analysis of yellow leaf coloration in Populus deltoides Marsh.

Populus deltoides Marsh has high ornamental value because its leaves remain yellow during the non-dormant period. However, little is known about the regulatory mechanism of leaf coloration in P. deltoides Marsh. Thus, we analyzed the physiological and transcriptional differences of yellow leaves (mutant) and green leaves (wild-type) of P. deltoides Marsh. Physiological experiments showed that the contents of chlorophyll (Chl) and carotenoid were lower in mutant leaves, and the flavonoid content did not differ significantly between mutant and wild-type leaves. Transcriptomic sequencing was further used to identify 153 differentially expressed genes (DEGs). Functional classifications based on Gene Ontology enrichment and Genome enrichment analysis indicated that the DEGs were involved in Chl biosynthesis and flavonoid biosynthesis pathways. Among these, geranylgeranyl diphosphate (CHLP) genes associated with Chl biosynthesis showed down-regulation, while chlorophyllase (CLH) genes associated with Chl degradation were up-regulated in yellow leaves. The expression levels of these genes were further confirmed using quantitative real-time PCR (RT-qPCR). Furthermore, the estimation of the main precursors of Chl confirmed that CHLP is a vital enzyme for the yellow leaf color phenotype. Consequently, the formation of yellow leaf color is due to the disruption of Chl synthesis or catabolism rather than flavonoid synthesis. These results contribute to our understanding of mechanisms and regulation of leaf color variation in poplar at the transcriptional level.

Candidate Genes for Yellow Leaf Color in Common Wheat (Triticum aestivum L.) and Major Related Metabolic Pathways according to Transcriptome Profiling.

The photosynthetic capacity and efficiency of a crop depends on the biosynthesis of photosynthetic pigments and chloroplast development. However, little is known about the molecular mechanisms of chloroplast development and chlorophyll (Chl) biosynthesis in common wheat because of its huge and complex genome. Ygm, a spontaneous yellow-green leaf color mutant of winter wheat, exhibits reduced Chl contents and abnormal chloroplast development. Thus, we searched for candidate genes associated with this phenotype. Comparative transcriptome profiling was performed using leaves from the yellow leaf color type (Y) and normal green color type (G) of the Ygm mutant progeny. We identified 1227 differentially expressed genes (DEGs) in Y compared with G (i.e., 689 upregulated genes and 538 downregulated genes). Gene ontology and pathway enrichment analyses indicated that the DEGs were involved in Chl biosynthesis (i.e., magnesium chelatase subunit H (CHLH) and protochlorophyllide oxidoreductase (POR) genes), carotenoid biosynthesis (i.e., β-carotene hydroxylase (BCH) genes), photosynthesis, and carbon fixation in photosynthetic organisms. We also identified heat shock protein (HSP) genes (sHSP, HSP70, HSP90, and DnaJ) and heat shock transcription factor genes that might have vital roles in chloroplast development. Quantitative RT-PCR analysis of the relevant DEGs confirmed the RNA-Seq results. Moreover, measurements of seven intermediate products involved in Chl biosynthesis and five carotenoid compounds involved in carotenoid-xanthophyll biosynthesis confirmed that CHLH and BCH are vital enzymes for the unusual leaf color phenotype in Y type. These results provide insights into leaf color variation in wheat at the transcriptional level.