Transcriptome Analysis Reveals Candidate Genes Associated with Leaf Etiolation of a Cytoplasmic Male Sterility Line in Chinese Cabbage (Brassica Rapa L. ssp. Pekinensis).

Fei Xie,Qing-Yong Yang,Zheng-Jie Wan,Jia-Lan Yuan,Jun-Hui Xia,Yi-Xiao Li,Hong-Yu Tang,Can-Jie Wang

doi:10.3390/ijms19040922

Fei Xie, Qing-Yong Yang + Show 6 more

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https://doi.org/10.3390/ijms19040922

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Abstract

Cytoplasmic male sterility (CMS) is universally utilized in cruciferous vegetables. However, the Chinese cabbage hau CMS lines, obtained by interspecific hybridization and multiple backcrosses of the Brassica juncea (B. juncea) CMS line and Chinese cabbage, show obvious leaf etiolation, and the molecular mechanism of etiolation remains elusive. Here, the ultrastructural and phenotypic features of leaves from the Chinese cabbage CMS line 1409A and maintainer line 1409B are analyzed. The results show that chloroplasts of 1409A exhibit abnormal morphology and distribution. Next, RNA-sequencing (RNA-Seq) is used to identify 485 differentially expressed genes (DEGs) between 1409A and 1409B, and 189 up-regulated genes and 296 down-regulated genes are found. Genes that affect chloroplasts development, such as GLK1 and GLK2, and chlorophyll biosynthesis, such as PORB, are included in the down-regulated DEGs. Quantitative real-time PCR (qRT-PCR) analysis validate that the expression levels of these genes are significantly lower in 1409A than in 1409B. Taken together, these results demonstrate that leaf etiolation is markedly affected by chloroplast development and pigment biosynthesis. This study provides an effective foundation for research on the molecular mechanisms of leaf etiolation of the hau CMS line in Chinese cabbage (Brassica rapa L. ssp. pekinensis).

Highlights

Chinese cabbage (Brassica rapa L. ssp. pekinensis; 2n = 20) belongs to the large Brassicaceae family and is one of the most widely planted leaf vegetables in China, where it originated
These results showed that the disturbance of chlorophyll biosynthesis or down-regulated expression of the PORB gene might be responsible for Pchlide homoeostasis and etiolated leaf [15]
Through RNA-Seq and biochemical analyses, we find that only the expression of PORB is down-regulated significantly in 1409A comparing to 1409B during chlorophyll synthesis

Summary

Introduction

Pekinensis; 2n = 20) belongs to the large Brassicaceae family and is one of the most widely planted leaf vegetables in China, where it originated. This crop is very rich in germplasm resources, and commercial producers currently have year-round production. The leaves of the CMS plants of Chinese cabbage exhibit a high degree of etiolation, turning almost yellow due to incompatibilities between the B. juncea sterile cytoplasm and the Brassica rapa (B. rapa) nucleus. Revealing the mechanism of leaf etiolation caused by the interspecific hybridization of B. juncea cytoplasmic sterile lines with Chinese cabbage and obtaining B. rapa plants with green sterile leaves are breeding goals

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