The plasma membrane H+-ATPase gene family in Solanum tuberosum L. Role of PHA1 in tuberization.

Margarita Stritzler,Juan Ignacio Cortelezzi,María Noelia Muñiz García,Daniela Andrea Capiati,Mariana Schlesinger

doi:10.1093/jxb/erx284

Abstract

This study presents the characterization of the plasma membrane (PM) H+-ATPases in potato, focusing on their role in stolon and tuber development. Seven PM H+-ATPase genes were identified in the Solanum tuberosum genome, designated PHA1-PHA7. PHA genes show distinct expression patterns in different plant tissues and under different stress treatments. Application of PM H+-ATPase inhibitors arrests stolon growth, promotes tuber induction, and reduces tuber size, indicating that PM H+-ATPases are involved in tuberization, acting at different stages of the process. Transgenic potato plants overexpressing PHA1 were generated (PHA1-OE). At early developmental stages, PHA1-OE stolons elongate faster and show longer epidermal cells than wild-type stolons; this accelerated growth is accompanied by higher cell wall invertase activity, lower starch content, and higher expression of the sucrose-H+ symporter gene StSUT1. PHA1-OE stolons display an increased branching phenotype and develop larger tubers. PHA1-OE plants are taller and also present a highly branched phenotype. These results reveal a prominent role for PHA1 in plant growth and development. Regarding tuberization, PHA1 promotes stolon elongation at early stages, and tuber growth later on. PHA1 is involved in the sucrose-starch metabolism in stolons, possibly providing the driving force for sugar transporters to maintain the apoplastic sucrose transport during elongation.

Highlights

Plasma membrane (PM) H+-ATPases are integral membrane proteins that pump protons out of the cell, generating an electrochemical gradient of protons across the plasmalemma
This study presents a comprehensive overview of the PM H+-ATPase gene family (PHA) in potato, including the identification of PHA genes and expression profiles to explore which PHA genes are possibly involved in tuberization
A search in the Potato Genome Sequencing Consortium database, revealed the existence of seven sequences presenting a high degree of homology with PM H+-ATPases in the S. tuberosum Phureja genome, designated PHA1–PHA7 (Supplementary Fig. S1; Supplementary Table S2)

Summary

Introduction

Plasma membrane (PM) H+-ATPases are integral membrane proteins that pump protons out of the cell, generating an electrochemical gradient of protons across the plasmalemma. PM H+-ATPase activity was determined in purified membranes isolated by a two-step aqueous two-phase partitioning system as described in Olivari et al (2000) from leaves of potato plants grown in soil for 60 d or stolons cultured in vitro on MS medium plus 8% sucrose for 3 weeks.

Results

Conclusion