Root-zone-specific sensitivity of K+ -and Ca2+ -permeable channels to H2O2 determines ion homeostasis in salinized diploid and hexaploid Ipomoea trifida

Abstract

Polyploids generally possess superior K+ /Na + homeostasis under saline conditions compared with their diploid progenitors. In this study, we identified the physiological mechanisms involved in the ploidy-related mediation of K+ /Na + homeostasis in the roots of diploid (2x) and hexaploid (6x; autohexaploid) Ipomoea trifida, which is the closest relative of cultivated sweet potato. Results showed that 6x I. trifida retained more K+ and accumulated less Na + in the root and leaf tissues under salt stress than 2x I. trifida. Compared with its 2x ancestor, 6x I. trifida efficiently prevents K+ efflux from the meristem root zone under salt stress through its plasma membrane (PM) K+ -permeable channels, which have low sensitivity to H2O2. Moreover, 6x I. trifida efficiently excludes Na + from the elongation and mature root zones under salt stress because of the high sensitivity of PM Ca2+ -permeable channels to H2O2. Our results suggest the root-zone-specific sensitivity to H2O2 of PM K+ - and Ca2+ -permeable channels in the co-ordinated control of K+ /Na + homeostasis in salinized 2x and 6x I. trifida. This work provides new insights into the improved maintenance of K+ /Na + homeostasis of polyploids under salt stress.