Comparative Cytological and Transcriptome Analyses of Anther Development in Nsa Cytoplasmic Male Sterile (1258A) and Maintainer Lines in Brassica napus Produced by Distant Hybridization

Abstract

1258A is a new line of B.napus with Nsa cytoplasmic male sterility (CMS) with potential applications in hybrid rapeseed breeding. Sterile cytoplasm was obtained from XinJiang Sinapis arvensis through distant hybridization and then backcrossed with 1258B for many generations. However, the characteristics and molecular mechanisms underlying pollen abortion in this sterile line are poorly understood. In this study, a cytological analysis revealed normal microsporogenesis and uninucleate pollen grain formation. Pollen abortion was due to non-programmed cell death in the tapetum and the inability of microspores to develop into mature pollen grains. Sucrose, soluble sugar, and adenosine triphosphate (ATP) contents during microspore development were lower than those of the maintainer line, along with an insufficient energy supply, reduced antioxidant enzyme activity, and substantial malondialdehyde (MDA) accumulation in the anthers. Transcriptome analysis revealed that genes involved in secondary metabolite biosynthesis, glutathione metabolism, phenylpropane biosynthesis, cyanoamino acid metabolism, starch and sucrose metabolism, and glycerolipid metabolism may contribute to pollen abortion. The down regulation of nine cytochrome P450 monooxygenases genes were closely associated with pollen abortion. These results suggest that pollen abortion in 1258A CMS stems from abnormalities in the chorioallantoic membranes, energy deficiencies, and dysfunctional antioxidant systems in the anthers. Our results provide insight into the molecular mechanism underlying pollen abortion in Nsa CMS and provide a theoretical basis for better heterosis utilization in B.napus.

Comparative study on abortion characteristics of Nsa CMS and Pol CMS and analysis of long non-coding RNAs related to pollen abortion in Brassica napus

“…The anthers of different sizes of 1258A and P5A were made into semi-thin sections to observe the process of pollen abortion. The preparation and staining methods of semi-thin sections were carried out according to the experimental method of Xing et al [ 35 ]. The semi-thin sections of pollen at different developmental stages were observed by optical microscope (Olympus CX51, Olympus Corporation, Tokyo, Japan).…”

“…An NEBNext® Ultra™ RNA Library Prep Kit for Illumina® (NEB, Ipswich, MA, USA) was used to construct mRNA-Seq and lncRNA-Seq libraries. Total RNA sample requirements and RNA-seq library construction methods were carried out according to the experimental method of Xing et al [ 35 ]. RNA-Seq was performed on an Illumina Hi-Seq platform by Beijing BoaoJingdian Biotechnology Co., Ltd. (Beijing, China).…”

“…arvensis ) and "Xiangyou15" ( B . napus ) [ 34 , 35 ]. The results of cytological observation showed that Nsa CMS uninucleate pollen grains all aborted and could not develop into mature pollen grains [ 35 – 37 ].…”

High‐temperature stress in crops: male sterility, yield loss and potential remedy approaches

“…In Brassica napus, Tang et al (2019) found a role for WRKY, MADS, MYB, HSP and NFHY transcription factors in creating male fertility during HT stress by using omics technology. Xing et al (2022) found the nine cytochrome P450 monooxygenases genes in pollen grains have a role in creating male fertility under HT stress. In tomato, heat shock transcription factor (HsfA2) was found by Fragkostefanakis et al (2016) to have a role in acquiring thermotolerance under HT stress condition by using omics technologies.…”

“…Xing et al . (2022) found the nine cytochrome P450 monooxygenases genes in pollen grains have a role in creating male fertility under HT stress. In tomato, heat shock transcription factor (HsfA2) was found by Fragkostefanakis et al .…”