Figure 6. rss1 affects cytokinin action.

(a) The exogenous application of cytokinins alleviated the lethality of rss1 under high-salt conditions. The basal shoot segments without roots (2.5 cm long) were excised from 1-week-old WT and rss1-2 plants, transferred to the medium containing 150 mM NaCl with or without the indicated concentrations of kinetin, and grown for 19 days. Bars, 5 cm. (b) The expression of CKX2 (top) and RR1 (bottom) in the basal shoot tissues of 1-week-old WT and rss1-2 seedlings, as determined by microarray analysis (magenta), or of WT and rss1-1 plants, as determined by quantitative RT-PCR (yellow). Seedlings grown under the normal (−NaCl) and saline (+NaCl) conditions were tested. The expression levels of the tested genes quantified by RT-PCR were normalized with that of ubiquitin E2. Mean±s.d., n=3. Asterisks, a significant difference between WT and rss1-2 under the saline condition. (P=0.002 (by real-time RT-PCR), P=0.001 (by microarray); one-tailed t-test). (c) A schematic illustration of the metabolic pathway of trans-zeatin (tZ) adapted from previous reports33,34. tZR, tZ riboside; tZRMP, tZR 5′-monophosphate; tZOG, tZ-O-glucoside; tZROG, tZ O-glucoside riboside; tZ7G, tZ-N-7-glucoside; CKX, cytokinin oxidase. (d) The levels of tZ and related metabolites in the 1-cm-long shoot basal tissues from 1-week-old seedlings of WT (blue and magenta) and rss1-2 seedlings (yellow and light blue) grown in the absence (blue and yellow) or presence of 150 mM NaCl (magenta and light blue) (mean±s.d., n=3). ND(1), the average of two independent samples due to one value being below the detection limit. ND(3), all values were below the detection limit in triplicate samples.