Tapetum-Dependent Male Meiosis Progression in Plants: Increasing Evidence Emerges

Xiaoning Lei,Bing Liu

doi:10.3389/fpls.2019.01667

Abstract

In higher plants, male meiosis is a key process during microsporogenesis and is crucial for male fertility and seed set. Meiosis involves a highly dynamic organization of chromosomes and cytoskeleton and specifically takes place within sexual cells. However, studies in multiple plant species have suggested that the normal development of tapetum, the somatic cell layer surrounding the developing male meiocytes, is indispensable for the completion of the male meiotic cell cycle. Disrupted tapetum development causes alterations in the expression of a large range of genes involved in male reproduction. Moreover, recent experiments suggest that small RNAs (sRNAs) present in the anthers, including microRNAs (miRNAs) and phased, secondary, small interfering RNAs (phasiRNAs), play a potential but important role in controlling male meiosis, either by influencing the expression of meiotic genes in the meiocytes or through other unclear mechanisms, supporting the hypothesis that male meiosis is non-cell autonomously regulated. In this mini review, we summarize the recorded meiotic defects that occur in plants with defective tapetum development in both Arabidopsis and crops. Thereafter, we outline the latest understanding on the molecular mechanisms that potentially underpin the tapetum-dependent regulation of male meiosis, and we especially discuss the regulatory role of sRNAs. At the end, we propose several outstanding questions that should be addressed in future studies.

Highlights

Male meiosis is a specialized type of cell division that gives rise to daughter cells with a reduced chromosome number
The male meiocytes in udt1 have normal chromosome dynamics, but dyads cannot develop into the tetrad stage, suggesting that the udt1 mutation-induced tapetum lesions primarily impact meiosis II. These findings indicate that a normal formation of the tapetum cell layer and its development at early anther stages are of essential importance for the undergoing and maturation of male meiosis
A PHD domain transcription protein, Tapetum Degeneration Retardation (TDR) Interacting Protein 3 (TIP3), was recently reported, and it plays a role in tapetum PCD and pollen development by regulating the expression of genes required for tapetum layer initiation and degeneration, including Multiple Sporocyte 1 (MSP1), GAMYB, Undeveloped Tapetum 1 (UDT1), TDR, and Eternal Tapetum1 (EAT1) (Yang et al, 2019d)

Summary

Introduction

Male meiosis is a specialized type of cell division that gives rise to daughter cells with a reduced chromosome number. These findings indicate that a normal formation of the tapetum cell layer and its development at early anther stages are of essential importance for the undergoing and maturation of male meiosis.

Results

Conclusion