Flower Development and Sex Determination between Male and Female Flowers in Vernicia fordii.

Yingji Mao,Lifang Wu,Yuting Wang,Jun Ni,Weili Lu,Jinyan Hou,Wenbo Liu,Yang Xu,Xue Chen

doi:10.3389/fpls.2017.01291

Abstract

Vernicia fordii is a monoecious and diclinous species with male and female flowers on the same inflorescence. Low female to male flower ratio is one of the main reasons for low yield in this species. However, little is known of its floral development and sex determination. Here, according to the results of scanning electron microscopy and histological analysis, the floral development of V. fordii was divided into 12 stages and the first morphological divergence between the male and female flowers was found to occur at stage 7. The male flowers are always unisexual, but the female flowers present bisexual characteristics, with sterile stamen (staminode) restricted to pre-meiosis of mother sporogenous cells and cell death occurring at later development stages. To further elucidate the molecular mechanism underling sex determination at the divergence stage for male and female flowers, comparative transcriptome analysis was performed. In total, 56,065 unigenes were generated and 608 genes were differentially expressed between male and female flowers, among which 310 and 298 DEGs (differentially expressed genes) showed high expression levels in males and females, respectively. The transcriptome data showed that the sexual dimorphism of female flowers was affected by jasmonic acid, transcription factors, and some genes related to the floral meristem activity. Ten candidate genes showed consistent expression in the qRT-PCR validation and DEGs data. In this study, we provide developmental characterization and transcriptomic information for better understanding of the development of unisexual flowers and the regulatory networks underlying the mechanism of sex determination in V. fordii, which would be helpful in the molecular breeding of V. fordii to improve the yield output.

Highlights

Two lakhs fifty thousand to Three lakhs fifty thousand flowering plants are known in the world, about 90% of which are hermaphroditic, producing male and female sex organs on the same flower, while 10% are completely unisexual (Charlesworth and Guttman, 1999; Paton et al, 2008; Heijmans et al, 2012; Renner, 2014)
Once transitioned to the reproductive stage, the SAM developed into an inflorescence shoot apical meristem (IM), which was subtended by bracts
The development of inflorescences started from July and lasted until April of the following year (Figure 1). This long period of inflorescence bud development can be seen in many species, such as pistachio (Pistacia vera), Chinese ixora (Ixora chinensis), and apples (Malus domestica) (Golan-Goldhirsh et al, 1998; Chen et al, 2003; Foster et al, 2003)

Summary

Introduction

Two lakhs fifty thousand to Three lakhs fifty thousand flowering plants are known in the world, about 90% of which are hermaphroditic, producing male and female sex organs on the same flower, while 10% are completely unisexual (Charlesworth and Guttman, 1999; Paton et al, 2008; Heijmans et al, 2012; Renner, 2014). Half of these unisexual plants are monoecious. The mechanisms of sex determination have been investigated in some model plants, such as maize and cucumber, and are mainly affected by genetics, plant hormones and environmental factors (Bai and Xu, 2013; Li and Liu, 2017)

Methods

Results

Conclusion