Genome-Wide Analysis and Expression Profiling of the JAZ Gene Family in Response to Abiotic Stress in Alfalfa

The Jasmonate ZIM-domain (JAZ) proteins act as repressors in the Jasmonate (JAs) signaling pathway, and play a critical role in regulating plant growth, development, and responses to biotic and abiotic stresses. In this study, bioinformatics methods were employed to identify the <i>JAZ</i> gene family in the whole genome of alfalfa (<i>Medicago sativa</i> cv. Zhongmu No. 1) and systematically analyze their gene characteristics, subcellular localization, phylogenetic evolution, promoter <i>cis</i>-elements, expression patterns, and responses to abiotic stress. A total of nine <i>MsJAZ</i> gene family members with complete TIFY and Jas domains were identified; they were distributed unevenly across four chromosomes and encoding proteins ranging from 94 aa (MsJAZ2) to 337 aa (MsJAZ7), with molecular weights (MWs) from 19.33 to 38.03 kDa. Phylogenetic analysis showed that the <i>MsJAZ</i> gene family could be classified into four clades (Clades I-II, IV-V), which are closely related to citrus. Most <i>MsJAZ</i> family members contain light-responsive, hormone-responsive, and stress-responsive <i>cis</i>-elements. Subcellular localization results indicated that all <i>MsJAZ</i> genes are expressed and function in the nucleus. The RT-qPCR results showed that <i>MsJAZ</i> genes were primarily expressed in the leaves and petioles. Under salt and drought stress, all <i>MsJAZ</i> genes exhibited varying degrees of response, with <i>MsJAZ4</i> and <i>MsJAZ7</i> showing the most pronounced reactions. Meanwhile, under chromium (Cr) and MeJA stress, both <i>MsJAZ4</i> and <i>MsJAZ9</i> exhibited strong responses. Subcellular localization results showed that the MsJAZ4/7 protein was localized on the plasma membrane and nucleus. The yeast adversity test showed that the <i>MsJAZ4/7</i> gene was more sensitive to salt stress. This study provides a foundation for future research on the function of the <i>MsJAZ</i> genes and its regulatory mechanism, as well as for identifying candidate genes for alfalfa stress tolerance breeding.