Spatiotemporally regulated callose deposition is an essential, genetically programmed phenomenon that promotes pollen development and functionality. Severe male infertility is associated with deficient callose biosynthesis, highlighting the significance of intact callose deposition in male gametogenesis. The molecular mechanism that regulates the crucial role of callose in production of functional male gametophytes remains completely unexplored. Here, we provide evidence that the gradual upregulation of a previously uncharacterized cotton (Gossypium hirsutum) pollen-specific SKS-like protein (PSP231), specifically at the post pollen-mitosis stage, activates callose biosynthesis to promote pollen maturation. Aberrant PSP231 expression levels caused by either silencing or overexpression resulted in late pollen developmental abnormalities and male infertility phenotypes in a dose-dependent manner, highlighting the importance of fine-tuned PSP231 expression. Mechanistic analyses revealed that PSP231 plays a central role in triggering and fine-tuning the callose synthesis and deposition required for pollen development. Specifically, PSP231 protein sequesters the cellular pool of RNA-binding protein GhRBPL1 to destabilize GhWRKY15 mRNAs, turning off GhWRKY15-mediated transcriptional repression of GhCalS4/GhCalS8 and thus activating callose biosynthesis in pollen. This study showed that PSP231 is a key molecular switch that activates the molecular circuit controlling callose deposition toward pollen maturation and functionality and thereby safeguards agricultural crops against male infertility.

时空调节的胼胝质沉积是一种重要的、基因编程的现象，可促进花粉发育和功能。严重的男性不育与胼胝质生物合成缺陷有关，凸显了完整的胼胝质沉积在雄性配子发生中的重要性。调节胼胝质在功能性雄性配子体产生中的关键作用的分子机制仍然完全未被探索。在这里，我们提供的证据表明，先前未表征的棉花（ Gossypium hirsutum ）花粉特异性SKS样蛋白（PSP231）的逐渐上调，特别是在花粉有丝分裂后阶段，激活胼胝质生物合成以促进花粉成熟。沉默或过度表达引起的PSP231表达水平异常会导致晚期花粉发育异常和男性不育表型，并呈剂量依赖性，这凸显了微调PSP231表达的重要性。机制分析表明，PSP231 在触发和微调花粉发育所需的胼胝质合成和沉积方面发挥着核心作用。具体来说，PSP231 蛋白隔离 RNA 结合蛋白 GhRBPL1 的细胞池，使GhWRKY15 mRNA 不稳定，关闭 GhWRKY15 介导的GhCalS4 / GhCalS8转录抑制，从而激活花粉中的胼胝质生物合成。这项研究表明，PSP231 是一个关键的分子开关，可激活控制胼胝质沉积以促进花粉成熟和功能的分子电路，从而保护农作物免受男性不育的影响。