Diversity in growth and expression pattern of PoHKT1 and PoVHA transporter genes under NaCl stress in Portulaca oleracea taxa

Abstract

Plant growth and the expression of two transporter genes; PoHKT1 and PoVHA transcripts in root and shoot tissues were studied under salt stress of three Portulaca oleracea s.l. taxa. The study showed no significant differences in ratios between root lengths in saline and non-saline treatments of the three taxa, which was correlated with a clear down-regulation of the PoHKT1 transcripts in the root after 150mM NaCl. All measured growth parameters except root length increased in P. oleraceae, decreased in P. granulatostellulata and remain unchanged after 100mM NaCl in P. nitida compared to control under saline conditions. The result was consistent with the type of taxon which had significant effect on the shoot length, number of leaves and dry weight (P< 0.05). All measured growth parameters except root length showed a significant negative correlation with the shoot fold change of PoHKT1 transcripts (r = -0.607, -0.693 and -0.657 respectively). The regulation of PoVHA in root and shoot tissues in the three taxa are significantly different. Under salt stress, both decreased uptake of Na+ into the cytosol by decreasing the expression of PoHKT1 and increased vascular compartmentalization ability of Na+ by inducing the expression of PoVHA seem to work more efficiently in P. oleraceae and P. nitida than in P. granulato-stellulata.