Involvement of a universal amino acid synthesis impediment in cytoplasmic male sterility in pepper.

Xianping Fang,Wei-Guo Chai,Zhen-Hui Gong,Hong-Fei Fu

doi:10.1038/srep23357

Abstract

To explore the mechanisms of pepper (Capsicum annuum L.) cytoplasmic male sterility (CMS), we studied the different maturation processes of sterile and fertile pepper anthers. A paraffin section analysis of the sterile anthers indicated an abnormality of the tapetal layer and an over-vacuolization of the cells. The quantitative proteomics results showed that the expression of histidinol dehydrogenase (HDH), dihydroxy-acid dehydratase (DAD), aspartate aminotransferase (ATAAT), cysteine synthase (CS), delta-1-pyrroline-5-carboxylate synthase (P5CS), and glutamate synthetase (GS) in the amino acid synthesis pathway decreased by more than 1.5-fold. Furthermore, the mRNA and protein expression levels of DAD, ATAAT, CS and P5CS showed a 2- to 16-fold increase in the maintainer line anthers. We also found that most of the amino acid content levels decreased to varying degrees during the anther tapetum period of the sterile line, whereas these levels increased in the maintainer line. The results of our study indicate that during pepper anther development, changes in amino acid synthesis are significant and accompany abnormal tapetum maturity, which is most likely an important cause of male sterility in pepper.

Highlights

To explore the cause of the abnormal development of the tapetal-layer cells and study the Cytoplasmic male sterility (CMS) molecular mechanisms using comprehensive biochemical and molecular biological methods
Our results showed that in the pollen mother cell stage, the sterile and maintainer lines did not present significant difference in their cytological structure, whereas a significant difference was observed in the CMS line beginning in the tetrad period of meiosis, after which pollen abortion occurs
Other results have shown that the pepper CMS line begins to degrade after the tetrad stage[43,44], which is consistent with our results

Summary

Introduction

To explore the cause of the abnormal development of the tapetal-layer cells and study the CMS molecular mechanisms using comprehensive biochemical and molecular biological methods. Compared with the results obtained through 2DE/DIGE, we will obtain better high-throughput and reproducible results using liquid chromatography-tandem mass spectrometry (LC-MS/MS). This process is labour intensive, investigating proteome changes during pepper anther development will provide meaningful data for further explorations of pepper CMS mechanisms. Many scientists have studied the changes in free amino acid content during anther development in fertile and CMS plants. We observed changes in the major metabolic pathways during the anther tapetal layer stage between the CMS line and the maintainer line and have further reported the relevant mechanisms of pepper CMS, which will help elucidate pepper CMS for use in heterosis breeding

Methods

Results

Conclusion