Male sterility is an important agronomical trait in self-pollinating plants for producing cost-effective F1 hybrids to harness the heterosis. Still, large-scale development and maintenance of male sterile lines and restoring fertility in F1 hybrids pose significant challenges in plant hybrid breeding. Cotton is a self-pollinating crop and exhibits strong hybrid vigor. However, there are currently few breeding methods to achieve cost-effective production of F1 hybrid cotton. Here, we utilized novel functions of the Arabidopsis autophagy-related BECLIN1/ATG6 and a mutant of E3 ubiquitin ligase COP1 (COP1^L105A) genes in developing rescuable male sterility in cotton. We have generated multiple male-sterile (MS) and restorer (RS) cotton lines expressing BECLIN1 and COP1^L105A, respectively. Cytological observation showed that post-meiotic tapetal expression of BECLIN1 delays tapetum developmental programmed cell death (dPCD) by affecting reactive oxygen species (ROS) balance—this delay in dPCD results in early microspore defects and later small-sized flowers with indehiscent anthers. Furthermore, the evaluation of F1 hybrids developed by crossing MS and RS lines showed that early tapetal COP1^L105A expression abolishes expression of BECLIN1 resulting in normal tapetum degeneration, pollen development, and fertility. In addition, the F1 hybrid developed with MS and RS cotton lines in transgenic glass-house and net-house conditions showed the rescued fertility comparable with control plants (WT). In terms of cotton fiber productivity, the COP1^L105A-expressing transgenic cotton lines outperformed the WT. The current work effectively demonstrates the wider applicability of the new F1 cotton production system.

中文翻译：

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花药绒毡层变性的时空调节为棉花中可逆的雄性不育系统铺平了道路


雄性不育是自花授粉植物的一个重要农艺性状，用于生产具有成本效益的 F1 杂交种以利用优势。尽管如此，雄性不育系的大规模开发和维持以及 F1 杂交种的生育能力恢复对植物杂交育种构成了重大挑战。棉花是一种自花授粉作物，具有很强的杂交活力。然而，目前很少有育种方法可以实现 F1 杂交棉的成本效益生产。在这里，我们利用拟南芥自噬相关 BECLIN1/ATG6 和 E3 泛素连接酶 COP1 （COP1^L105A） 基因的突变体的新功能在棉花中开发可挽救的雄性不育。我们已经生产了多个雄性不育 （MS） 和恢复体 （RS） 棉品系，分别表达 BECLIN1 和 COP1^L105A。细胞学观察表明，BECLIN1减数分裂后绒毡层的表达通过影响活性氧 （ROS） 平衡来延迟绒毡层发育程序性细胞死亡 （dPCD）——dPCD 的这种延迟导致早期小孢子缺陷和后来的小花，花药不开裂。此外，通过杂交 MS 和 RS 系开发的 F1 杂交种的评估表明，早期绒毡层 COP1^L105A 表达消除了 BECLIN1 的表达，导致正常的绒毡层变性、花粉发育和生育能力。此外，在转基因温室和网房条件下用 MS 和 RS 棉花品系开发的 F1 杂交种显示出与对照植物 （WT） 相当的挽救生育力。在棉纤维生产力方面，表达 COP1^L105A 的转基因棉花品系优于 WT。目前的工作有效地证明了新的 F1 棉花生产系统具有更广泛的适用性。