Zhou Lian, Vejlupkova Zuzana, Warman Cedar, Fowler John E
Maize Research Institute, College of Agronomy and Biotechnology, Southwest University, Chongqing, China.
Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, United States.
Front Plant Sci. 2021 Feb 25;12:635244. doi: 10.3389/fpls.2021.635244. eCollection 2021.
Members of the La-related protein family (LARPs) contain a conserved La module, which has been associated with RNA-binding activity. Expression of the maize gene GRMZM2G323499/Zm00001d018613, a member of the LARP family, is highly specific to pollen, based on both transcriptomic and proteomic assays. This suggests a pollen-specific RNA regulatory function for the protein, designated ZmLARP6c1 based on sequence similarity to the LARP6 subfamily in . To test this hypothesis, a transposable element insertion in the gene () was obtained from the Dooner/Du mutant collection. Sequencing confirmed that the insertion is in an exon, and thus likely interferes with ZmLARP6c1 function. Tracking inheritance of the insertion via its endosperm-expressed GFP indicated that the mutation was associated with reduced transmission from a heterozygous plant when crossed as a male (ranging from 0.5 to 26.5% transmission), but not as a female. Furthermore, this transmission defect was significantly alleviated when less pollen was applied to the silk, reducing competition between mutant and wild-type pollen. Pollen grain diameter measurements and nuclei counts showed no significant differences between wild-type and mutant pollen. However, , mutant pollen tubes were significantly shorter than those from sibling wild-type plants, and also displayed altered germination dynamics. These results are consistent with the idea that ZmLARP6c1 provides an important regulatory function during the highly competitive progamic phase of male gametophyte development following arrival of the pollen grain on the silk. The conditional, competitive nature of the male sterility phenotype (i.e., reduced ability to produce progeny seed) points toward new possibilities for genetic control of parentage in crop production.
La相关蛋白家族（LARPs）的成员包含一个保守的La模块，该模块与RNA结合活性有关。基于转录组学和蛋白质组学分析，玉米基因GRMZM2G323499/Zm00001d018613（LARP家族的一个成员）的表达对花粉具有高度特异性。这表明该蛋白具有花粉特异性RNA调节功能，根据其与文献中LARP6亚家族的序列相似性，将其命名为ZmLARP6c1。为了验证这一假设，从Dooner/Du突变体库中获得了该基因（）中的一个转座子插入。测序证实该插入位于一个外显子中，因此可能会干扰ZmLARP6c1的功能。通过其胚乳表达的绿色荧光蛋白追踪该插入的遗传情况表明，当作为父本杂交时，该突变与杂合植物的传递减少有关（传递率在0.5%至26.5%之间），但作为母本时则没有。此外，当给花丝施加较少花粉时，这种传递缺陷得到了显著缓解，减少了突变花粉与野生型花粉之间的竞争。花粉粒直径测量和细胞核计数显示野生型和突变型花粉之间没有显著差异。然而，突变型花粉管明显短于其野生型同胞植株的花粉管，并且发芽动态也有所改变。这些结果与以下观点一致，即ZmLARP6c在花粉粒落在花丝上后雄配子体发育的高度竞争的受精前阶段提供了重要的调节功能。该雄性不育表型的条件性、竞争性本质（即产生后代种子的能力降低）为作物生产中亲子关系的遗传控制指明了新的可能性。
