Figure 7.

Repression of MT2b Expression Induces Epidermal Cell Death.

(A) Stem sections of rice cv Nipponbare were treated with or without (control) 150 μM ethephon for 0, 26, or 48 h, and epidermal cell death rates (percentage of epidermal patches that showed blue staining) were determined with Evans Blue staining. Results are means (±se) from 11 to 31 stems analyzed. Cell death rates were significantly elevated after treatment with 150 μM ethephon for 48 h (P < 0.001; Tukey test).

(B) Stem sections of the rice cv Nipponbare insertion mutant MT2b∷Tos17 were treated as in (A). Results are means (±se) from 17 to 36 stems analyzed per time point and treatment. Cell death rates were significantly elevated in MT2b∷Tos17 over cell death rates in the wild type (A) at each time point and treatment analyzed. Cell death rates in the MT2b∷Tos17 mutant were significantly higher after treatment with 150 μM ethephon for 26 and 48 h compared with untreated (control) stems (P < 0.001; Tukey test).

(C) RNA gel blot analysis of MT2b expression in the second youngest leaf of 16-week-old rice cv Kinmaze plants in the wild type and two lines transformed with an MT2b-RNAi construct. As a control for RNA loading, rRNA was stained with ethidium bromide.

(D) Wild-type and MT2b-RNAi lines 3 and 5 were treated with 150 μM ethephon for 26 h, and epidermal cell death rates were determined with Evans Blue staining. Results are means (±se) from 18 to 27 stem sections analyzed per genotype and treatment. The basal cell death rate in line 3 was significantly higher than in the wild type or line 5 at P < 0.05 (Tukey test).