Journal: Journal of Experimental Botany
Article Title: Root-zone-specific sensitivity of K+-and Ca2+-permeable channels to H2O2 determines ion homeostasis in salinized diploid and hexaploid Ipomoea trifida
Figure Lengend Snippet: Schematic model of the mediation of root K + /Na + homeostasis in the response of 2 x and 6 x I. trifida to NaCl stress (solid arrows indicate the ion flux direction and width reflects flux magnitude). In all root regions, NaCl stress results in a similar activation of PM H + -ATPase activity in 2 x and 6 x I. trifida , causing a similar K + loss through depolarization-activated K + channels. The increment in cytosolic Na + triggers an elevation of cytosolic Ca 2+ and stimulates NADPH oxidase activity, resulting in H 2 O 2 accumulation within the cells or in the apoplast and activating a series of H 2 O 2 -specific K + - and Ca 2+ -permeable channels. In the meristem zone, the lower sensitivity of K + -permeable channels to H 2 O 2 contributes to the lower K + loss in 6 x I. trifida . The drastic K + loss in the meristem zone of 2 x I. trifida may trigger the longitudinal transport of K + to regain the optimal K + level of the meristematic cells, thereby causing the K + deprivation at the whole-root level. In the elongation and mature zones, the increased sensitivity of Ca 2+ -permeable channels to H 2 O 2 causes a robust Ca 2+ influx through the H 2 O 2 -activated Ca 2+ -permeable channels, thereby triggering stronger Na + /H + antiport activity across the PM in 6 x I. trifida . Charge imbalance caused by the Ca 2+ influx may be offset by the OH . -activated K + efflux. Hence, the K + /Na + homeostasis in root tissues is retained in salinized 6 x I. trifida .
Article Snippet: Root tips (3 cm) were collected from non-treated or NaCl-treated 2x and 6x I. trifida and were incubated in staining buffer containing 5 mM KCl/MES and 3 μg ml−1 PI (Life Technologies, Carlsbad, CA, USA) for 20 min.
Techniques: Activation Assay, Activity Assay