Genome-wide identification of Argonaute family genes in Cucumis melo L. and characterization of their expression profiles upon different developmental and stressful clues

Argonaute (AGO) proteins are highly conserved in living organisms and play pivotal roles in gene silencing. In contrast to a myriad of published work about AGOs in Arabidopsis and model crops such as rice and tomato, this protein family has never been globally explored in melon ( Cucumis melo L.). In this study, a total of 7 AGO members distributed on 5 chromosomes were uncovered in melon genome, together with their key physicochemical parameters of genomic sequence, coding sequence and protein length, as well as molecular weight and theoretical isoelectric point. Structural prediction showed that, in addition to the signature domains (PAZ and PIWI), variable number of disordered regions, particularly those potentially related to liquid-liquid phase separation (LLPS) process, were observed in CmAGOs, suggesting that LLPS might serves as a novel regulatory layer for AGO biological activities. Collinearity and phylogenetic investigation pointed to the evolutionarily diversification of CmAGO members from non-cucurbitaceae plants, particularly grass species, indicating their functional specification over long-term domestication. Moreover, we found that the promoter regions of CmAGO s were overrepresented by multiple cis -acting elements potentially associated with melon growth, development and adaption to stressful conditions, which were partially supported by RNA-seq and qPCR assays. Altogether, these findings expand our knowledge about AGO family in plants and could benefit functional investigation of CmAGOs in future.