Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, 94720, USA.
Plant J. 2013 Nov;76(4):592-602. doi: 10.1111/tpj.12318. Epub 2013 Oct 5.
Male fertility in flowering plants relies on proper division and differentiation of cells in the anther, a process that gives rise to four somatic layers surrounding central germinal cells. The maize gene male sterility32 (ms32) encodes a basic helix-loop-helix (bHLH) transcription factor, which functions as an important regulator of both division and differentiation during anther development. After the four somatic cell layers are generated properly through successive periclinal divisions, in the ms32 mutant, tapetal precursor cells fail to differentiate, and, instead, undergo additional periclinal divisions to form extra layers of cells. These cells become vacuolated and expand, and lead to failure in pollen mother cell development. ms32 expression is specific to the pre-meiotic anthers and is distributed initially broadly in the four lobes, but as the anther develops, its expression becomes restricted to the innermost somatic layer, the tapetum. The ms32-ref mac1-1 double mutant is unable to form tapetal precursors and also exhibits excessive somatic proliferation leading to numerous, disorganized cell layers, suggesting a synergistic interaction between ms32 and mac1. Altogether, our results show that MS32 is a major regulator in maize anther development that promotes tapetum differentiation and inhibits periclinal division once a tapetal cell is specified.
在有花植物中，雄性育性依赖于花药中细胞的正确分裂和分化，这一过程产生了围绕中央生殖细胞的四个体细胞层。玉米雄性不育 32 号基因（ms32）编码一个碱性螺旋-环-螺旋（bHLH）转录因子，它是花药发育过程中细胞分裂和分化的重要调节因子。在四个体细胞层通过连续的平周分裂正确产生后，在 ms32 突变体中，绒毡层前体细胞不能分化，而是进行额外的平周分裂，形成额外的细胞层。这些细胞变得空泡化并扩张，导致花粉母细胞发育失败。ms32 的表达是特异于减数分裂前的花药，最初广泛分布在四个裂片中，但随着花药的发育，其表达变得局限于最内层的体细胞层，即绒毡层。ms32-ref mac1-1 双突变体不能形成绒毡层前体细胞，也表现出过多的体细胞增殖，导致许多组织混乱的细胞层，这表明 ms32 和 mac1 之间存在协同相互作用。总之，我们的结果表明，MS32 是玉米花药发育中的一个主要调节因子，它促进绒毡层的分化，并在一个绒毡层细胞被特化后抑制平周分裂。
