In flowering plants, double fertilization between male and female gametophytes, which are separated by distance, largely depends on the unique pattern of the male gametophyte (pollen): two non‐motile sperm cells suspended within a tube‐producing vegetative cell. A morphological screen to elucidate the genetic control governing the strategic patterning of pollen has led to the isolation of a sticky generative cell (sgc) mutant that dehisces abnormal pollen with the generative cell immobilized at the pollen wall. Analyses revealed that the sgc mutation is specifically detrimental to pollen development, causing ectopic callose deposition that impedes the timely internalization and differentiation of the generative cell. We found that the SGC gene encodes the highly conserved domain of unknown function 707 (DUF707) gene that is broadly expressed but is germline specific during pollen development. Additionally, transgenic plants co‐expressing fluorescently fused SGC protein and known organelle markers showed that SGC localizes in the endoplasmic reticulum, Golgi apparatus and vacuoles in pollen. A yeast two‐hybrid screen with an SGC bait identified a thaumatin‐like protein that we named GCTLP1, some homologs of which bind and/or digest β‐1,3‐glucans, the main constituent of callose. GCTLP1 is expressed in a germline‐specific manner and colocalizes with SGC during pollen development, indicating that GCTLP1 is a putative SGC interactor. Collectively, our results show that SGC suppresses callose deposition in the nascent generative cell, thereby allowing the generative cell to fully internalize into the vegetative cell and correctly differentiate as the germline progenitor, with the potential involvement of the GCTLP1 protein, during pollen development in Arabidopsis.

中文翻译：

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粘性生殖细胞突变体的分析表明，抑制生殖细胞中的胼胝质沉积是拟南芥生殖细胞内化和分化所必需的

在开花植物中，相隔距离的雄性和雌性配子体之间的双重受精在很大程度上取决于雄性配子体（花粉）的独特模式：两个不能运动的精子细胞悬浮在产生管的营养细胞中。阐明控制花粉战略模式的遗传控制的形态学筛选导致分离出粘性生殖细胞( sgc ) 突变体，该突变体使异常花粉裂开，生殖细胞固定在花粉壁上。分析表明，sgc突变特别不利于花粉发育，导致异位胼胝质沉积，阻碍生殖细胞的及时内化和分化。我们发现SGC基因编码高度保守的功能未知域 707 (DUF707) 基因，该基因广泛表达但在花粉发育过程中具有种系特异性。此外，共表达荧光融合 SGC 蛋白和已知细胞器标记的转基因植物表明，SGC 位于内质网、高尔基体和花粉中的液泡中。带有 SGC 诱饵的酵母双杂交筛选鉴定了一种我们命名为 GCTLP1 的奇异果甜蛋白样蛋白，其中一些同源物结合和/或消化 β-1,3-葡聚糖，β-1,3-葡聚糖是胼胝质的主要成分。GCTLP1 以种系特异性方式表达，并在花粉发育过程中与 SGC 共定位，表明 GCTLP1 是假定的 SGC 相互作用因子。总的来说，我们的结果表明 SGC 抑制了新生生殖细胞中的胼胝质沉积，