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Title: Transcriptomic identification and expression of starch and sucrose metabolism genes in the seeds of chinese chestnut (Castanea mollissima)

Author
item ZHANG, LIN - Central South University Of Forestry And Technology
item LIN, QING - Central South University Of Forestry And Technology
item FENG, YANZHI - China Paulowniz Research Center
item FAN, XIAOMING - Central South University Of Forestry And Technology
item ZOU, FENG - Central South University Of Forestry And Technology
item YUAN, DE-YI - Central South University Of Forestry And Technology
item ZENG, XIAOCHUN - Collaborator
item Cao, Heping

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2014
Publication Date: 12/22/2014
Citation: Zhang, L., Lin, Q., Feng, Y., Fan, X., Zou, F., Yuan, D., Zeng, X., Cao, H. 2014. Transcriptomic identification and expression of starch and sucrose metabolism genes in the seeds of chinese chestnut (Castanea mollissima). Journal of Agricultural and Food Chemistry. 63(3):929-942. https://doi.org/10.1021/jf505247d.
DOI: https://doi.org/10.1021/jf505247d

Interpretive Summary: Chinese chestnut (Castanea mollissima) is a member of the Fagaceae family native to China, Taiwan and Korea. The tree is widely cultivated in eastern Asia. Over 300 cultivars have been selected for nut production. The nuts are rich in nutrients and used as an important starch food in rural diets. The chestnut wood also provides economical values of the tree. Chestnuts are good for human health as an alternative gluten-free flour source and also a rich source of other beneficial compounds. Starch is the major metabolite in chestnuts. However, starch biosynthesis was not studied in chestnut. This study aimed to evaluate metabolite profiles and identify genes coding for important enzymes in starch and sucrose metabolism by transcriptome and quantitative real-time polymerase chain reaction (qPCR). Metabolite analysis showed that starch was the major component and rapidly accumulated during seed development. Amylopectin was approximately three-fold of amylose content in chestnut starch. Starch and sucrose metabolism contained 141 unigenes including one for glycogenin glucosyltransferase, three for ADP-glucose pyrophosphorylase, eight for starch synthase, two for branching enzyme, eleven for sucrose synthase and three for sucrose-phosphate synthase. Among them, 56 unigenes showed = 2-fold of expression difference between the 45 and 75 DAF seeds. The expression of 21 unigenes putatively coding for major enzymes in starch and sucrose metabolism was validated by qPCR using RNA from five stages of seeds. Expression profiles and correlation analysis indicated that the mRNA levels of AGP (large and small subunits), granule-bound SS2, soluble SS1 and SS4 were well-correlated with starch accumulation in the seeds. This study provides valuable metabolite and transcriptome resources for future research in starch and sucrose metabolism in Chinese chestnut tree.

Technical Abstract: The Chinese chestnut (Castanea mollissima) seed provides a rich source of carbohydrates as food and feed. However, little is known about starch biosynthesis in the seeds. The objectives of this study were to determine seed composition profiles and identify genes involved in starch and sucrose metabolism. Metabolite analysis showed that starch was the major component and rapidly accumulated during seed development. Amylopectin was approximately three-fold of amylose content in chestnut starch. Illumina platform-based transcriptome sequencing generated 56,671 unigenes in two cDNA libraries from seeds collected at 45 and 75 days after flowering (DAF). 1,537 unigenes showed expression differences = 2-fold in the two stages of seeds including 570 upregulated and 967 down-regulated unigenes. We identified 141 unigenes involved in starch and sucrose metabolism, including one for glycogenin glucosyltransferase, three for ADP-glucose pyrophosphorylase (AGP), eight for starch synthase (SS), two for starch branching enzyme, eleven for sucrose synthase, and three for sucrose-phosphate synthase. Among them, 56 unigenes showed a = 2-fold expression difference between the 45 and 75 DAF seeds including 10 up- and 46 down-regulated unigenes. In addition, transcripts for 18 and 15 unigenes were detected predominantly in 45 and 75 DAF seeds, respectively. The expression of 21 unigenes putatively coding for major enzymes in starch and sucrose metabolism was validated by qPCR using RNA from five seed stages. Expression profiles and correlation analysis indicated that the mRNA levels of AGP (large and small subunits), granule-bound SS2, soluble SS1 and SS4 were well-correlated with starch accumulation in the seeds. This study provides valuable metabolite and transcriptome resources for future research in starch and sucrose metabolism in Chinese chestnut tree.