School of Life Sciences and Biotechnology, The Joint International Research Laboratory of Metabolic and Developmental Sciences, Joint Center for Single Cell Biology, Shanghai Jiao Tong University, Shanghai, 200240, China.
School of Agriculture and Biology, Joint Center for Single Cell Biology, Shanghai Jiao Tong University, Shanghai, 200240, China.
J Integr Plant Biol. 2022 Mar;64(3):702-716. doi: 10.1111/jipb.13197. Epub 2022 Feb 28.
Ovule initiation is a key step that strongly influences ovule number and seed yield. Notably, mutants with enhanced brassinosteroid (BR) and cytokinin (CK) signaling produce more ovules and have a higher seed number per silique (SNS) than wild-type plants. Here, we crossed BR- and CK-related mutants to test whether these phytohormones function together in ovule initiation. We determined that simultaneously enhancing BR and CK contents led to higher ovule and seed numbers than enhancing BR or CK separately, and BR and CK enhanced each other. Further, the BR-response transcription factor BZR1 directly interacted with the CK-response transcription factor ARABIDOPSIS RESPONSE REGULATOR1 (ARR1). Treatments with BR or BR plus CK strengthened this interaction and subsequent ARR1 targeting and induction of downstream genes to promote ovule initiation. Enhanced CK signaling partially rescued the reduced SNS phenotype of BR-deficient/insensitive mutants whereas enhanced BR signaling failed to rescue the low SNS of CK-deficient mutants, suggesting that BR regulates ovule initiation and SNS through CK-mediated and -independent pathways. Our study thus reveals that interaction between BR and CK promotes ovule initiation and increases seed number, providing important clues for increasing the seed yield of dicot crops.
胚珠起始是一个关键步骤，强烈影响胚珠数量和种子产量。值得注意的是，增强油菜素内酯（BR）和细胞分裂素（CK）信号的突变体比野生型植物产生更多的胚珠，并且每一个蒴果中的种子数量更高（SNS）。在这里，我们将 BR 和 CK 相关突变体进行杂交，以测试这些植物激素是否在胚珠起始中共同起作用。我们确定，同时增强 BR 和 CK 的含量会导致胚珠和种子数量高于单独增强 BR 或 CK，并且 BR 和 CK 相互增强。此外，BR 反应转录因子 BZR1 直接与 CK 反应转录因子 ARABIDOPSIS RESPONSE REGULATOR1（ARR1）相互作用。BR 或 BR 加 CK 的处理增强了这种相互作用以及随后的 ARR1 靶向和诱导下游基因以促进胚珠起始。增强的 CK 信号传导部分挽救了 BR 缺陷/不敏感突变体中降低的 SNS 表型，而增强的 BR 信号传导未能挽救 CK 缺陷突变体中的低 SNS，这表明 BR 通过 CK 介导和非依赖途径调节胚珠起始和 SNS。因此，我们的研究表明，BR 和 CK 之间的相互作用促进了胚珠的起始，增加了种子数量，为提高双子叶作物的种子产量提供了重要线索。
