Overexpression of an Inositol Phosphorylceramide Glucuronosyltransferase Gene IbIPUT1 Inhibits Na+ Uptake in Sweet Potato Roots

Abstract

IPUT1 is a glycosyltransferase capable of synthesizing the glycosyl inositol phosphorylceramide (GIPC) sphingolipid. The GIPC sphingolipid is a Na+ receptor on cell membranes which can sense extracellular Na+ concentrations, promote the increase in intracellular Ca2+ concentrations, and plays critical roles in maintaining intracellular Na+ balance. Therefore, the IPUT1 gene plays an important role in the genetic improvement of crop salt tolerance. Herein, the IbIPUT1 gene, which encodes an ortholog of Arabidopsis AtIPUT1, from sweet potato was cloned. Agrobacterium rhizogenes-mediated in vivo transgenic technology, non-invasive micro-measuring technology (NMT) and Na+ fluorescence imaging technology were then combined to quickly study the potential function of IbIPUT1 in salt tolerance. The data showed that IbIPUT1 was involved in the regulation of root cell Na+ balance, and the overexpression of IbIPUT1 could not promote sweet potato root cell Na+ efflux under salt stress, but it could significantly inhibit the Na+ absorption of root cells, thereby reducing the accumulation of Na+ in root cells under salt stress. Additionally, Ca2+ efflux in transgenic root cells was slightly higher than that in control roots under salt stress. Collectively, an efficient transgenic method for gene function studies was established, and our results suggested that IbIPUT1 acts as a candidate gene for the genetic enhancement of sweet potato salt tolerance.