Legume Genomics and Genetics 2025, Vol.16, No.2, 63-71 http://cropscipublisher.com/index.php/lgg 66 3.2 Genomic distribution and chromosomal localization How are these WRKY genes distributed on the chromosomes of chickpeas? According to current research, the number is approximately between 61 and 78, and the results of different analyses vary slightly. For instance, a study analyzed 70 non-redundant WRKY genes and found that they were distributed on almost all chromosomes except chromosome 8 (Shende et al., 2021). This distribution is not concentrated and clustered but rather scattered, indicating that the WRKY gene is widely distributed throughout the genome. Another interesting finding is that during the amplification of the WRKY gene family, fragment repeats play a more significant role, while tandem repeats are less common. 3.3 Gene structure analysis and phylogenetic relationships The structures of different WRKY genes actually vary significantly. Some contain 2 to 7 introns, while a very few even have no introns at all. From the structural analysis, it can be seen that in addition to the WRKY conserved structural domain, there are also some group-specific motifs, which provide clues for their functional differentiation. After the evolutionary tree was constructed, the researchers classified these WRKY proteins into three major categories (I, II, III) and their further subcategories, in a classification manner similar to that of other plants. More importantly, this phylogenetic relationship not only helps clarify the evolutionary origins among genes, but also indicates that these genes have been subjected to certain purification selection pressure during amplification, especially those collateral homologous genes. 4WRKYGene Expression in Chickpea under Abiotic and Biotic Stresses 4.1 WRKYgene expression in response to drought and salinity In dry or saline-alkali environments, chickpeas do not completely "silence", and the WRKY transcription factor in their bodies is often rapidly activated. According to the results of transcriptome and whole-genome analysis, many WRKY members show upregulated expression in roots and stems, not only during drought but also under cold stress. However, the expression differences among different genotypes are still quite obvious. Under extreme drought conditions, the expression of the WRKY gene in drought-tolerant strains is often more intense, while in sensitive strains, although it is also upregulated, the extent is not as high. This implies a possibility: WRKY is very likely involved in the regulatory pathway that enhances the stress resistance of chickpeas. Of course, one point cannot be overlooked - not all members of WRKY were involved, and some members hardly changed under such coercion. 4.2 Role in pathogen defense (e.g., Fusarium, Ascochyta) It's not only environmental stress that triggers WRKY's response; when pathogenic bacteria come, they will also "step in". For instance, when chickpeas are attacked by Fusarium acuminatumor Trichospora, studies have found that the expression of many WRKY genes changes significantly, especially between disease-resistant and susceptible strains. Some members, like WRKY40, were significantly induced in resistant varieties, and its increased expression was usually accompanied by enhanced disease resistance (Chakraborty et al., 2018). In addition, some studies have focused on epigenetic regulatory mechanisms such as histone acetylation in the promoter region and found that they are also involved in the regulatory process of WRKY. More interestingly, when the WRKY gene of these chickpeas was transferred into model plants, the antibacterial ability of those plants was also enhanced (Priyadarshini et al., 2023). From this perspective, WRKY is not "fighting alone"; they might be an indispensable part of the pathogen defense system. 4.3 Tissue-specific and developmental expression patterns The WRKY gene is not expressed everywhere and functions at any time in chickpeas. Their "switches" are often linked to tissue type or developmental stage. Some are only active in the roots, while others are expressed only in the stems or specific leaf tissues. What is more complex is that some WRKY proteins exhibit similar expression profiles under various stress scenarios, suggesting that they may be involved in relatively universal response mechanisms. In contrast, there are also some that will only be activated under specific coercion. Such a "dual control of time and space" model enables chickpeas to flexibly respond to changes in the external environment, avoiding treating all stimuli equally and wasting resources.
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