Comprehensive transcriptome analysis of phytohormone biosyntheis and signaling genes in the flowers of Chinese chinquapin (Castanea henryi)

Authors: FAN, XIAOMING - Central South University Of Forestry And Technology; YUAN, DEYI - Central South University Of Forestry And Technology; TIAN, XIAOMING - Hunan Hybrid Rice Research Center; ZHU, ZHOUJUN - Central South University Of Forestry And Technology; LIU, MEILAN - Central South University Of Forestry And Technology; Cao, Heping

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2017
Publication Date: 11/29/2017
Citation: Fan, X., Yuan, D., Tian, X., Zhu, Z., Liu, M., Cao, H. 2017. Comprehensive transcriptome analysis of phytohormone biosyntheis and signaling genes in the flowers of Chinese chinquapin (Castanea henryi). Journal of Agricultural and Food Chemistry. 65(47):10332-10349.

Interpretive Summary: Castanea Miller (Fagaceae) is a monoecious plant genus with ecological and economic value. Castanea Miller species are cultured in many countries due to good taste and rich in nutrition of the nuts. However, the low ratio of female and male flowers is one of the reasons for the low seed yield of the species. Therefore, it is important to explore the mechanism of floral sex differentiation in the species; which may provide valuable information for increasing seed yield. Sex determination is under control by both genetic factors and environmental conditions. Although several phytohormones are known to have essential roles during gender differentiation, there is no inclusive study of their involvement in Castanea Miller species. In this study, we investigated several aspects of flowering and its regulation by plant hormones in Chinese chinquapin. We carried out the morphological observation of sex differentiation and flower development in C. henryi, analyzed the endogenous levels of four kinds of phytohormones in the flower and investigated the effects of four exogenous phytohormones on sex differentiation. We used transcriptome analysis to analyze cell type-specific expression profiles of the biosynthetic and signaling genes for these four phytohormones and validated the expression of 18 unigenes encoding key enzymes in the phytohormone biosynthesis pathway by qPCR using RNAs from four stages of C. henryi flower. The results suggest that several gnes may play key roles in phytohormone biosynthesis and sex differentiation of C. henryi. This study presents the first comprehensive report of phytohormone biosynthesis and signaling during sex differentiation of C. henryi, which should provide the foundation for further mechanistic studies of sex differentiation in Castanea Miller species and other non-model plants.

Technical Abstract: The Chinese chinquapin (Castanea henryi) nut provides a rich source of starch and nutrient elements as food and feed, but its yield is restricted by a low ratio of female to male flowers (1/2000-1/3000). Little is known about the developmental programs underlying the sex differentiation of the flowers. To investigate the involvement of phytohormones during C. henryi sex differentiation, we described the morphology of male and female floral organs and the cytology of flower sex differentiation, analyzed endogenous levels of indole-3-acetic acid (IAA), gibberellins (GAs), cytokinins (CKs) and abscisic acid (ABA) in the flowers, investigated the effects of exogenous hormones on flower development, and evaluated the expression profiles of genes related to the biosyntheses and signaling pathways of these four phytohormones using RNA-Seq combined with qPCR. Morphological results showed that C. henryi flowers consisted of unisexual and bisexual catkins, and could be divided into four developmental stages. HPLC results showed that CK accumulated much more in the female flower than that in the male flower, GA and ABA showed the opposite results, while IAA did not show a tendency. The effects of exogenous hormones on sex differentaiton in C. henryi were consistent with those of endogenous hormones. RNA-Seq combined with qPCR anlyses suggest that several gnes may play key roles in phytohormone biosynthesis and sex differentiation of C. henryi. This study presents the first comprehensive report of phytohormone biosynthesis and signaling during sex differentiation of C. henryi, which should provide the foundation for further mechanistic studies of sex differentiation in Castanea Miller species and other non-model plants.