Inflorescence abscission protein S1IDL6 promotes low light intensity-induced tomato flower abscission

Authors: LI, RUIZHEN - Shenyang Agricultural University; SHI, CHUN-LI - University Of Oslo; WANG, XIAOYANG - Shenyang Agricultural University; MENG, YAN - Shenyang Agricultural University; CHENG, LINA - Shenyang Agricultural University; Jiang, Cai-Zhong; QI, MINGFANG - Shenyang Agricultural University; XU, TAO - Shenyang Agricultural University; LI, TAINLAI - Shenyang Agricultural University

Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2021
Publication Date: 3/12/2021
Citation: Li, R., Shi, C., Wang, X., Meng, Y., Cheng, L., Jiang, C., Qi, M., Xu, T., Li, T. 2021. Inflorescence abscission protein S1IDL6 promotes low light intensity-induced tomato flower abscission. Plant Physiology. 186:1288-1301. https://doi.org/10.1093/plphys/kiab121.
DOI: https://doi.org/10.1093/plphys/kiab121

Interpretive Summary: Plants have the capacity to shed their vegetative and reproductive organs in response to developmental signals and environmental stimuli. While this abscission process has many adaptive benefits, in an agricultural context premature abscission can cause a major reduction in crop productivity, as exemplified by fruit set failure. Thus, there is considerable interest in understanding the mechanism of organ abscission and its regulation. Abscission is a highly regulated process involving structural, biochemical and molecular changes in a specialized area of the organ called the abscission zone (AZ). Multiple phytohormones are known to play roles in triggering and modulating abscission, and ethylene is a particularly well documented accelerator of leaf, flower and fruit abscission. Accordingly, enhancing ethylene production, and promoting ethylene signaling by elevating the expression of ethylene response genes, including transcription factor (TF) genes, have been shown to promote abscission. However, while WRKY TFs are known to function in integrating ethylene responses during senescence, their role in abscission is not well understood. In addition to ethylene, a small peptide, INFLORESCENCE DEFECIENT IN ABSCISSION (IDA), has been identified as an essential signaling element in the induction of A. thaliana flower abscission. However, the role of IDA signaling in tomato abscission and its relationship with ethylene is still unclear. In this study, we analyzed the expression patterns of an IDA-Like gene (SlIDL6) in low light-induced flower abscission, and used tandem mass spectrometry to identify and characterize the mature SlIDL6 peptide. Tomato knockout lines and Arabidopsis thaliana overexpression lines were created to investigate the in vivo function of the tomato peptide, and yeast one-hybrid assays were used to investigate binding of the SlWRKY17 transcription factor to the SlIDL6 promoter, and silencing of SlWRKY17 expression delayed low light-induced flower abscission. SlIDL6 was specifically expressed in the abscission zone (AZ) and at high levels during low light-induced abscission and ethylene treatment. SlIDL6 knockout lines showed delayed low light-induced flower drop, and application of SlIDL6 peptide accelerated abscission. Overexpression of SlIDL6 rescued the A. thaliana ida mutant phenotype suggesting functional conserved between species. SlIDL6-mediated abscission was found to act downstream of ethylene signaling. We report a SlWRKY17- SlIDL6 regulatory module that functions in low light promoted abscission through increasing the expression of cell wall remodeling and disassembly in an ethylene-dependent manner.

Technical Abstract: In many fruiting plant species, flower abscission is induced by low light stress. Here, we elucidated how signaling mediated by the peptide INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) controls low light-induced flower drop in tomato. We analyzed the expression patterns of an IDA-Like gene (SlIDL6) in low light-induced flower abscission, and used tandem mass spectrometry to identify and characterize the mature SlIDL6 peptide. Tomato knockout lines and Arabidopsis thaliana overexpression lines were created to investigate the in vivo function of the tomato peptide, and yeast one-hybrid assays were used to investigate binding of the SlWRKY17 transcription factor to the SlIDL6 promoter, and silencing of SlWRKY17 expression delayed low light-induced flower abscission. SlIDL6 was specifically expressed in the abscission zone (AZ) and at high levels during low light-induced abscission and ethylene treatment. SlIDL6 knockout lines showed delayed low light-induced flower drop, and application of SlIDL6 peptide accelerated abscission. Overexpression of SlIDL6 rescued the A. thaliana ida mutant phenotype suggesting functional conserved between species. SlIDL6-mediated abscission was found to act downstream of ethylene signaling. We report a SlWRKY17- SlIDL6 regulatory module that functions in low light promoted abscission through increasing the expression of cell wall remodeling and disassembly in an ethylene-dependent manner.