Deciphering the Role of Aquaporins Under Different Abiotic Stress Conditions in Watermelon (Citrullus lanatus)

Aquaporins (AQPs) play essential roles in various physiological processes by regulating the transport of water and various uncharged small solutes, like carbon dioxide, urea, and metalloids, including silicon (Si). In the present study, 35 AQPs were identified in the watermelon (Citrullus lanatus) genome and subsequently analyzed to understand their role and regulation during various abiotic stress conditions. For a better understanding of solute specificity, gene and protein structure of Citrullus lanatus AQPs (ClaAPQs) various computational tools were used. Based on the selectivity filters ClaNIP2-1 was characterized as Si transporter. Transcriptomics analysis revealed the expression of ClaAQPs under drought stress and during fruit development. In addition, differential expression of AQPs during drought, cold, salinity, and methyl jasmonate stress was observed with gene expression evaluated by quantitative real-time PCR (qRT-PCR). Interestingly, the expression of ClaTIP1-1 and ClaPIP2-4 was found to be increased during both cold and salinity stresses. In the early stages of stress, increased expression of ClaNIP2-1 and ClaPIP1-2 and ClaTIP1-1 was observed. The expression of ClaPIP1-2 was significantly increased at least once during methyl jasmonate, drought, salinity, and cold stress. The findings indicate that PIPs particularly ClaPIP1-2 and ClaPIP2-4 play a significant role in stress response. The information presented here will provide the fundamental basis of AQP-mediated transport system in watermelon and closely related Cucurbitaceae species.