Transcriptome Analyses Reveal Candidate Pod Shattering-Associated Genes Involved in the Pod Ventral Sutures of Common Vetch (Vicia sativa L.).

Rui Dong,Deke Dong,Wengang Xie,Qiang Zhou,Zhipeng Liu,Xutian Chai,Yanrong Wang,Wenxian Liu,Dong Luo,Yang Dong,Jiyu Zhang

doi:10.3389/fpls.2017.00649

Abstract

The seed dispersion caused by pod shattering is a form of propagation used by many wild species. Loss of seeds from pod shattering is frequent in the common vetch (Vicia sativa L.), an important self-pollinating annual forage legume. However, pod shattering is one of the most important defects that limits the reproduction of the vetch in the field and the usage as a leguminous forage crop. To better understand the vetch pod shattering mechanism, we used high-throughput RNA sequencing to assess the global changes in the transcriptomes of the pod ventral sutures of shattering-susceptible and shattering-resistant vetch accessions screened from 541 vetch germplasms. A total of 1,285 significantly differentially expressed unigenes (DEGs) were detected, including 575 up-regulated unigenes and 710 down-regulated unigenes. Analyses of Gene Ontology and KEGG metabolic enrichment pathways of 1,285 DEGs indicated that 22 DEGs encoding cell wall modifications and hydrolases associated with pod shattering were highly expressed in shattering-susceptible accessions. These genes were mainly enriched in “hydrolase activity,” “cytoplasm,” and “carbohydrate metabolic process” systems. These cell wall modifications and hydrolases genes included β-glucosidase and endo-polygalacturonase, which work together to break down the glycosidic bonds of pectin and cellulose, and to promote the dissolution and disappearance of the cell wall in the ventral suture of the pod and make the pod more susceptible to shattering. We demonstrated the differences in gene transcription levels between the shattering-susceptible and shattering-resistant vetch accessions for the first time and our results provided valuable information for the identifying and characterizing of pod shattering regulation networks in vetch. This information may facilitate the future identification of pod shattering-related genes and their underlying molecular mechanisms in the common vetch.

Highlights

In nature, seed dispersion or fruit dehiscence is an essential process in the proliferation of wild plants (Funatsuki et al, 2014)
By comparing the transcriptomes of the pod ventral sutures of shattering-susceptible and shatteringresistant accessions screened from 541 vetch accessions, the present study provides a good understanding of the genetic basis of pod shattering in the common vetch, which exhibits different dehiscence zone structures from those of Arabidopsis and soybeans
The results showed that the activities of polygalacturonase and cellulase (β-1,3;1,4-glucanase) were significantly higher in the pod ventral sutures of the shattering-susceptible accessions than in those of the shatteringresistant accessions (Figures 4, 5)

Summary

Introduction

In nature, seed dispersion or fruit dehiscence is an essential process in the proliferation of wild plants (Funatsuki et al, 2014). This process can be used to ensure adequate growth space for the progeny of plants in nature (Funatsuki et al, 2014) This agronomic trait exists in most Leguminosae, Gramineae, and Brassicaceae crops, such as common vetch (Vicia sativa L.) (Abd El-Moneim, 1993), soybeans (Glycine max L.) (Christiansen et al, 2002), rice (Oryza sativa L.) (Dong et al, 2014), thale cress (Arabidopsis thaliana L.) (Dong et al, 2014) and oilseed rape (Brassica napus L.) (del Carmen Rodríguez-Gacio et al, 2004). Resistance to pod shattering has been preferentially selected for during domestication as the most important domestication trait (Funatsuki et al, 2014)

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Discussion

Conclusion