Genomic Survey of Genes Encoding Major Intrinsic Proteins (MIPs) and Their Response to Arsenite Stress in Pepper (Capsicum annum)

Major intrinsic proteins (MIPs) are a super family of proteins that mediate the bidirectional concentration-dependent flux of water in particularly small solutes in fraction and some metalloids across the cell membrane. This article reports the genome-wide study of pepper genes encoding MIPs and their expression analysis. Using a bioinformatics homology search, 48 CAMIPs were identified on the genome of pepper. A total of 48 MIPs were further divided in sub classes as 22 CATIPs, 15 CAPIPs, 10 CANIPs, and 1 CASIP. The 48 Pepper MIP encoding genes were mapped on the 12 pepper chromosomes. CAMIP synteny analysis exhibited 17 duplicated genes, and these were clustered into eight tandem duplicated regions on pepper chromosomes. The tissue-specific expression of MIPs based on RNA-Seq showed certain CANIPs, CATIPs, and CAPIPs were highly expressed in roots, while some CATIPs and CASIPs were expressed in stem as well. As(III), at 0.5 and 1 mM, was applied to pepper plants, where 1 mM significantly reduced leaf chlorophyll content, leaf nitrogen content, and root length. To see which CAMIPs participate in As(III) transport, we tested the response of genes encoding MIPs to As(III) through qRT-PCR. As(III) uptake was observed in both shoot and root samples treated with 0.5 mM and 1 mM As(III) for 12 h and 24 h because of MIPs' quantitative response through qRT-PCR. Most of the MIPs were down-regulated in response to both levels of As(III); besides CANIPs, there were CATIPs and CAPIPs up-regulated in response to higher concentrations of As(III) in the roots and shoot, which suggests the involvement of CAMIPs in the uptake as well as detoxification mechanism in pepper against As(III). Unlike prokaryotes, plant MIPs have diverse selectivity for arsenite and other solutes. Our study provides important insights into the arsenite uptake and detoxification, offering a foundation for further functional and stress-tolerance studies.