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Transcriptomic analysis of Litchi chinensis pericarp during maturation with a focus on chlorophyll degradation and flavonoid biosynthesis.

ABSTRACT: The fruit of litchi (Litchi chinensis) comprises a white translucent edible aril surrounded by a pericarp. The pericarp of litchi has been the focus of studies associated with fruit size, coloration, cracking and shelf life. However, research at the molecular level has been limited by the lack of genomic and transcriptomic information. In this study, an analysis of the transcriptome of litchi pericarp was performed to obtain information regarding the molecular mechanisms underlying the physiological changes in the pericarp, including those leading to fruit surface coloration.Coincident with the rapid break down of chlorophyll, but substantial increase of anthocyanins in litchi pericarp as fruit developed, two major physiological changes, degreening and pigmentation were visually apparent. In this study, a cDNA library of litchi pericarp with three different coloration stages was constructed. A total of 4.7 Gb of raw RNA-Seq data was generated and this was then de novo assembled into 51,089 unigenes with a mean length of 737 bp. Approximately 70% of the unigenes (34,705) could be annotated based on public protein databases and, of these, 3,649 genes were significantly differentially expressed between any two coloration stages, while 156 genes were differentially expressed among all three stages. Genes encoding enzymes involved in chlorophyll degradation and flavonoid biosynthesis were identified in the transcriptome dataset. The transcript expression patterns of the Stay Green (SGR) protein suggested a key role in chlorophyll degradation in the litchi pericarp, and this conclusion was supported by the result of an assay over-expressing LcSGR protein in tobacco leaves. We also found that the expression levels of most genes especially late anthocyanin biosynthesis genes were co-ordinated up-regulated coincident with the accumulation of anthocyanins, and that candidate MYB transcription factors that likely regulate flavonoid biosynthesis were identified.This study provides a large collection of transcripts and expression profiles associated with litchi fruit maturation processes, including coloration. Since most of the unigenes were annotated, they provide a platform for litchi functional genomic research within this species.

SUBMITTER: Lai B

PROVIDER: S-EPMC4376514 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Transcriptomic analysis of Litchi chinensis pericarp during maturation with a focus on chlorophyll degradation and flavonoid biosynthesis.

Lai Biao B Hu Bing B Qin Yong-Hua YH Zhao Jie-Tang JT Wang Hui-Cong HC Hu Gui-Bing GB

BMC genomics 20150321

<h4>Background</h4>The fruit of litchi (Litchi chinensis) comprises a white translucent edible aril surrounded by a pericarp. The pericarp of litchi has been the focus of studies associated with fruit size, coloration, cracking and shelf life. However, research at the molecular level has been limited by the lack of genomic and transcriptomic information. In this study, an analysis of the transcriptome of litchi pericarp was performed to obtain information regarding the molecular mechanisms under ...[more]

PMID: 25887579

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Project description:Light is a key environmental factor that affects anthocyanin biosynthesis. To enhance our understanding of the mechanisms involved in light-regulated anthocyanin biosynthesis in the pericarp of litchi, we performed transcriptomic analyses on the basis of Illumina sequencing. Fruit clusters were bagged with double-layer Kraft paper bags at 42 days after anthesis. The bags were removed after 2 weeks. Under light conditions, anthocyanins accumulated rapidly in the pericarp. RNA sequences were de novo assembled into 75,935 unigenes with an average length of 913 bp. Approximately 74.5% of unigenes (56,601) were annotated against four public protein databases. A total of 16,622 unigenes that significantly differed in terms of abundance were identified. These unigenes are implicated in light signal perception and transduction, flavonoid biosynthesis, carotenoid biosynthesis, plant hormone signal transduction, and photosynthesis. In photoreceptors, the expression levels of UV RESISTANCE LOCUS 8 (UVR8), Phototropin 2 (PHOT2), Phytochrome B (PHYB), and Phytochrome C (PHYC) increased significantly when the fruits were exposed to light. This result indicated that they likely play important roles in anthocyanin biosynthesis regulation. After analyzed digital gene expression (DGE), we found that the light signal transduction elements of COP1 and COP10 might be responsible for anthocyanin biosynthesis regulation. After the bags were removed, nearly all structural and regulatory genes, such as UDP-glucose: flavonoid-3-O-glucosyltransferase (UFGT), MYB, basic helix-loop-helix (bHLH), and WD40, involved in the anthocyanin biosynthetic pathway were upregulated. In addition to MYB-bHLH-WD40 transcription complex, ELONGATED HYPOCOTYL (HY5), NAM/ATAF/CUC (NAC), homeodomain leucine zipper proteins (ATHBs), and FAR-RED ELONGATED HYPOCOTYL (FHY) possibly participate in light-induced responses. On the basis of DGEs and qRT-PCR validation, we observed a light-induced anthocyanin biosynthesis and regulation pattern in litchi pericarp. This study enhanced our understanding of the molecular mechanisms governing light-induced anthocyanin biosynthesis in litchi pericarp.

Project description:Litchi has diverse fruit color phenotypes, yet no research reflects the biochemical background of this diversity. In this study, we evaluated 12 litchi cultivars for chromatic parameters and pigments, and investigated the effects of abscisic acid, forchlorofenron (CPPU), bagging and debagging treatments on fruit coloration in cv. Feizixiao, an unevenly red cultivar. Six genes encoding chalcone synthase (CHS), chalcone isomerase (CHI), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR), anthocyanidin synthase (ANS) and UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) were isolated from the pericarp of the fully red litchi cv. Nuomici, and their expression was analyzed in different cultivars and under the above mentioned treatments. Pericarp anthocyanin concentration varied from none to 734 mg m(-2) among the 12 litchi cultivars, which were divided into three coloration types, i.e. non-red ('Kuixingqingpitian', 'Xingqiumili', 'Yamulong'and 'Yongxing No. 2'), unevenly red ('Feizixiao' and 'Sanyuehong') and fully red ('Meiguili', 'Baila', Baitangying' 'Guiwei', 'Nuomici' and 'Guinuo'). The fully red type cultivars had different levels of anthocyanin but with the same composition. The expression of the six genes, especially LcF3H, LcDFR, LcANS and LcUFGT, in the pericarp of non-red cultivars was much weaker as compared to those red cultivars. Their expression, LcDFR and LcUFGT in particular, was positively correlated with anthocyanin concentrations in the pericarp. These results suggest the late genes in the anthocyanin biosynthetic pathway were coordinately expressed during red coloration of litchi fruits. Low expression of these genes resulted in absence or extremely low anthocyanin accumulation in non-red cultivars. Zero-red pericarp from either immature or CPPU treated fruits appeared to be lacking in anthocyanins due to the absence of UFGT expression. Among these six genes, only the expression of UFGT was found significantly correlated with the pericarp anthocyanin concentration (r?=?0.84). These results suggest that UFGT played a predominant role in the anthocyanin accumulation in litchi as well as pericarp coloration of a given cultivar.

Project description:In Arabidopsis, treating shoots with uniconazole can result in enhanced primary root elongation and bolting delay. Uniconazole spraying has become an important cultivation technique in controlling the flowering and improving the fruit-setting of litchi. However, the mechanism by which uniconazole regulates the complicated developmental processes in litchi remains unclear. This study aimed to determine which signal pathways and genes drive the responses of litchi inflorescences to uniconazole treatment. We monitored the transcriptional activity in inflorescences after uniconazole treatment by Illumina sequencing technology. The global expression profiles of uniconazole-treated litchi inflorescences were compared with those of the control, and 4051 differentially expressed genes were isolated. KEGG pathway enrichment analysis indicated that the plant hormone signal transduction pathway served key functions in the flower developmental stage under uniconazole treatment. Basing on the transcriptional analysis of genes involved in flower development, we hypothesized that uniconazole treatment increases the ratio of female flowers by activating the transcription of pistil-related genes. This phenomenon increases opportunities for pollination and fertilization, thereby enhancing the fruit-bearing rate. In addition, uniconazole treatment regulates the expression of unigenes involved in numerous transcription factor families, especially the bHLH and WRKY families. These findings suggest that the uniconazole-induced morphological changes in litchi inflorescences are related to the control of hormone signaling, the regulation of flowering genes, and the expression levels of various transcription factors. This study provides comprehensive inflorescence transcriptome data to elucidate the molecular mechanisms underlying the response of litchi flowers to uniconazole treatment and enumerates possible candidate genes that can be used to guide future research in controlling litchi flowering.

Dataset Information

Transcriptomic analysis of Litchi chinensis pericarp during maturation with a focus on chlorophyll degradation and flavonoid biosynthesis.

Publications

Transcriptomic analysis of Litchi chinensis pericarp during maturation with a focus on chlorophyll degradation and flavonoid biosynthesis.

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