A SlCLV3-SlWUS module regulates auxin and ethylene homeostasis in low light–induced tomato flower abscission

背景回顾：Premature abscission of flowers and fruits triggered by low light stress can severely reduce crop yields. 

提出问题：However, the underlying molecular mechanism of this organ abscission is not fully understood. 

结果1-CLV3表达模式：Here, we show that a gene (SlCLV3) encoding CLAVATA3 (CLV3), a peptide hormone that regulates stem cell fate in meristems, is highly expressed in the pedicel abscission zone (AZ) in response to low light in tomato (Solanum lycopersicum). 

结果2-CLV3敲除表型：SlCLV3 knockdown and knockout lines exhibit delayed low light–induced flower drop. 

结果3-CLV3-CLV1/BAM1-WUS：The receptor kinases SlCLV1 and BARELY ANY MERISTEM1 (SlBAM1) function in the SlCLV3 peptide–induced low light response in the AZ to decrease expression of the transcription factor gene WUSCHEL (SlWUS).

结果4-WUS-KD1/FUL2：DNA affinity purification sequencing identified the transcription factor genes KNOX-LIKE HOMEDOMAIN PROTEIN1 (SlKD1) and FRUITFULL2 (SlFUL2) as SlWUStarget genes. 

结果5-作用机制：Our data reveal that low light reduces SlWUS expression, resulting in higher SlKD1 and SlFUL2 expression in the AZ, thereby perturbing the auxin response gradient and causing increased ethylene production, eventually leading to the initiation of abscission. 

结论：These results demonstrate that the SlCLV3-SlWUS signaling pathway plays a central role in low light–induced abscission by affecting auxin and ethylene homeostasis.

 摘 要 

低光照胁迫导致的花和果实提前脱落会严重降低作物的产量。然而，这种器官脱落的潜在分子机制尚不完全清楚。本文中，作者发现番茄中一个调控干细胞命运的多肽编码基因SlCLV3响应于低光照，在花梗脱落区高表达。SlCLV3基因的敲低和敲除株系在低光照胁迫下，表现出延迟的花脱落表型。在花梗脱落区，受体激酶SlCLV1和SlBAM1作用于SlCLV3多肽诱导低光照响应，以减少转录因子SlWUS基因的表达。DAP-seq结果表明，转录因子SlKD1和SlFUL2是SlWUS的靶基因。本文的研究结果表明，低光照降低了SlWUS基因的表达，导致花梗脱落区中SlKD1和SlFUL2的表达增加，从而扰乱生长素响应梯度以及增加了乙烯的产量，最终导致花器官的脱落。这些研究结果表明，SlCLV3-SlWUS信号通路通过影响生长素和乙烯的内稳态，在低光照诱导的器官脱落中发挥核心作用。

 李天来