Aquaporin genes in garden pea and their regulation by the nano-antioxidant fullerol in imbibing embryos under osmotic stress

Abstract

Aquaporins (AQPs) are known as small membrane intrinsic proteins that help to transport water and certain solutes through biological membranes. AQPs gene families are being extensively studied in major crops, but less investigated in pea (<italic>Pisum sativum</italic> L.), which is an economically significant legume crop with a huge complex genome. Here, we present a genome-wide identification, structural characterization, subcellular localization, and expression profiling of the AQPs in pea with a particular interest in their involvement in nano fullerol-conferred osmotic stress alleviation. We identified 39 full-length aquaporin genes from the pea genome, which were classified into five subfamilies. The protein structure of aquaporins appears to have substrate-specific residues which are conserved in plants, allowing for inference of substrate specificity. In particular, the PsNIP2-2-2 was identified with a Gly-Ser-Gly-Arg (GSGR) selective filter that indicates the ability to uptake silicon. Analysis of tissue transcriptomes revealed preferred expressions of certain <italic>PsAQPs</italic> in the underground, aerial and reproductive organs, respectively. Development-regulated expressions of two <italic>PsTIPs</italic> and two <italic>PsPIPs</italic> in seeds were noticed. RNA-Seq of the imbibing embryos treated with mannitol (M) or mannitol plus 100 mg/L fullerol (MF) revealed two <italic>PsTIPs</italic> being similarly regulated by M or MF, three <italic>PsNIPs</italic> being up-regulated only by M without F, and four other genes that were only regulated under MF condition. To our knowledge, this is the first report on transcriptional regulation of AQPs by fullerols, which adds to our knowledge on the plant-carbon nano-substances interactions.