A Silent Exonic Mutation in a Rice Integrin-α FG-GAP Repeat-Containing Gene Causes Male-Sterility by Affecting mRNA Splicing.

Ting Zou,Yang Tao,Dan Zhou,Shuangcheng Li,Aijun Wang,Aiping Zheng,Qiming Deng,Lingxia Wang,Zhiyuan He,Xu Zhang,Huainian Liu,Shiquan Wang,Jun Zhu,Wenjie Li,Ping Li,Yueyang Liang,Guoqiang Yuan

doi:10.3390/ijms21062018

Abstract

Pollen development plays crucial roles in the life cycle of higher plants. Here we characterized a rice mutant with complete male-sterile phenotype, pollen-less 1 (pl1). pl1 exhibited smaller anthers with arrested pollen development, absent Ubisch bodies, necrosis-like tapetal hypertrophy, and smooth anther cuticular surface. Molecular mapping revealed a synonymous mutation in the fourth exon of PL1 co-segregated with the mutant phenotype. This mutation disrupts the exon-intron splice junction in PL1, generating aberrant mRNA species and truncated proteins. PL1 is highly expressed in the tapetal cells of developing anther, and its protein is co-localized with plasma membrane (PM) and endoplasmic reticulum (ER) signal. PL1 encodes an integrin-α FG-GAP repeat-containing protein, which has seven β-sheets and putative Ca2+-binding motifs and is broadly conserved in terrestrial plants. Our findings therefore provide insights into both the role of integrin-α FG-GAP repeat-containing protein in rice male fertility and the influence of exonic mutation on intronic splice donor site selection.

Highlights

Pollen, as the male gametophyte, plays key roles in flowering plant fertilization for giving rise to fruits and seeds [1]
Pollen development begins with pollen mother cells (PMCs) that differentiated from sporogenous cells in developing anthers [2]
The results revealed that PL1 transcripts were highly accumulated in developing spikelets with anthers from stages 4 to 12 and were reached the maximum amount in spikelets with anthers at stages 9 and 10 (Figure 5I), when the tapetum programmed cell death (PCD) and pollen wall formation began (Zhang and Wilson, 2009; Zhang et al, 2011)

Summary

Introduction

As the male gametophyte, plays key roles in flowering plant fertilization for giving rise to fruits and seeds [1]. After two steps of meiosis, PMCs develop into microspores [3]. At this stage, microspores are surrounded with a thin primexine, and the depositions of sporopollenin precursors on undulated PM for exine formation initiate thereafter [4,5]. As the microspores go through vacuolation and two rounds of mitosis afterwards, the formation of mature pollen grains, which are coated by two-layered exine and fulfilled of inclusions, is completed [6–8]. The developmental processes of pollen occur inside of the anther, which consists of four somatic cell layers, namely, the tapetum, middle layer, endothecium and outer epidermis [6,9,10]. The tapetum is the innermost cell layer of the anther wall and directly contacts with the developing microspores and secrets enzymes, nutrition, sporopollenin precursors and developmental signals [11,12]. As a skin of anther, cuticle locates on the surface of anther epidermis and acts as a barrier to protect pollen development from external biotic or abiotic stress [15,16]

Methods

Results

Conclusion