Overexpression of Two CCCH-type Zinc-Finger Protein Genes Leads to Pollen Abortion in Brassica campestris ssp. chinensis.

Liai Xu,Jiashu Cao,Xingpeng Xiong,Weimiao Liu,Youjian Yu,Tingting Liu

doi:10.3390/genes11111287

Liai Xu, Jiashu Cao + Show 4 more

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https://doi.org/10.3390/genes11111287

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Abstract

The pollen grains produced by flowering plants are vital for sexual reproduction. Previous studies have shown that two CCCH-type zinc-finger protein genes in Brassica campestris, BcMF30a and BcMF30c, are involved in pollen development. Due to their possible functional redundancy, gain-of-function analysis is helpful to reveal their respective biological functions. Here, we found that the phenotypes of BcMF30a and BcMF30c overexpression transgenic plants driven by their native promoters were similar, suggesting their functional redundancy. The results showed that the vegetative growth was not affected in both transgenic plants, but male fertility was reduced. Further analysis found that the abortion of transgenic pollen was caused by the degradation of pollen contents from the late uninucleate microspore stage. Subcellular localization analysis demonstrated that BcMF30a and BcMF30c could localize in cytoplasmic foci. Combined with the studies of other CCCH-type genes, we speculated that the overexpression of these genes can induce the continuous assembly of abnormal cytoplasmic foci, thus resulting in defective plant growth and development, which, in this study, led to pollen abortion. Both the overexpression and knockout of BcMF30a and BcMF30c lead to abnormal pollen development, indicating that the appropriate expression levels of these two genes are critical for the maintenance of normal pollen development.

Highlights

In flowering plants, each microspore mother cell in the anthers undergoes meiosis to produce four haploid microspores, which are initially associated in a tetrad
In order to further determine at which stage of pollen development they are expressed, and whether they are expressed in other tissues, we used previously obtained transgenic plants containing ProBcMF30a:GUS or ProBcMF30c:GUS for further expression analysis
The results revealed that the numbers of pollen tubes that grew in BcMF30aOE and BcMF30cOE pistils were equivalent to those in the control plants after self-pollination (Figure 6D–F)

Summary

Introduction

Each microspore mother cell in the anthers undergoes meiosis to produce four haploid microspores, which are initially associated in a tetrad. The microspores separate from each other and undergo vacuolation and expansion, and the nuclei within them migrate toward the cell wall. Pollen mitosis I (PMI) yields a bicellular pollen (BCP) composed of a larger vegetative cell (VC) and a smaller generative cell (GC) that is engulfed by VC. The GC further yields two sperm cells after a symmetric division (PMII), and results in a tricellular pollen (TCP) grain. Genes 2020, 11, 1287 and their expression levels change as development progresses [1]. This clearly illustrates that this series of pollen development events is regulated by dynamic and complex changes in gene expression

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