Figure 7
RSS1 interacts with known regulators of elongation growth. (a) Yeast two-hybrid assays of interactions between RSS1 and BEE2 or HBI1 proteins. (b) RSS1 transcript levels were slightly reduced in bee1, 2, 3 triple mutants. (c) RSS1 overexpression highly represses BEE2 transcript abundance. (d,e) Effect of HBI1 overexpression on RSS1 transcript abundance and vice versa. Overexpressing HBI1 caused induction of RSS1 whereas RSS1OE2 leads to HBI1 transcript repression suggesting a negative interaction between both these proteins. (f) The hypocotyl elongation phenotypes of rss1 mutant were similar to 35 s:HBI1:YFP seedlings further confirming a negative correlation between RSS1 and HBI1 functions. The hypocotyl elongation phenotype of RSS1OE2 seedlings was similar to that of 35 s:IBH1 seedlings suggesting that RSS1 might possess functional similarity to IBH1. Analysis of EODFR induced hypocotyl elongation growth response in WT, 35 s:HBI1:YFP, bee1,2,3 and 35 s:IBH1 seedlings growing on (g) ½ MS medium (1% Suc) and (h) ½ MS medium supplemented without or with different Glc concentrations (0%, 1%, 3%, 5% w/v). The HBI1 overexpressing mutants showed constitutively more hypocotyl elongation and increased sensitivity towards EODFR whereas the IBH1 overexpressing seedlings showed reduced hypocotyl elongation and resistance towards EODFR treatment. Expression values represent the average of two biological replicates with three technical replicates each. Physiological data shown is the average of two biological replicates each having atleast 15 seedlings; error bars represent SE; (Student’s t-test; P < 0.01; *control vs. treatment; **WT vs. mutant).
