Figure 3.

GA and MYBGA Antagonize the Sugar Repression of Nuclear Import of MYBS1 and α-Amylase Expression.

(A) Barley aleurones were transfected with Ubi:GFP-OsMYBS1 and incubated in +S medium for 24 h. GA₃ was then added, and aleurones were incubated for another 24 and 48 h.

(B) Transgenic rice aleurones carrying Ubi:OsMYBGA were transfected with Ubi:GFP-OsMYBS1 and incubated in +S or −S medium for 24 h.

(C) Aleurones of gamyb-2 mutant seeds were transfected with Ubi:GFP-OsMYBS1 and incubated in +S or −S medium for 24 h. Next, GA₃ was added, and aleurones were incubated for another 24 h.

Images of fluorescent fields and composites of fluorescent and bright fields are shown in (A) and (B). Vacuolation was observed in GA₃-treated or MYBGA-overexpressing aleurone cells but not in GA₃-treated gamyb-2 aleurone cells. The nucleus is distorted due to overlap with enlarged vacuoles. C and N indicate higher GFP signals and c and n indicate lower GFP signals in the cytoplasm and nucleus, respectively. See also Supplemental Figure 5 online.

(D) to (F) Accumulation of αAmy8, MYBGA, and MYBS1 mRNA in aleurones of wild-type (WT), MYBGA-overexpressing transgenic, and gamyb-2 mutant rice. Rice aleurone layers were incubated in +S or −S medium with or without GA₃ for 24 h. Total RNA was purified and subjected to quantitative RT-PCR analysis. MYBGA mRNA was undetectable in the gamyb-2 mutant.

[See online article for color version of this figure.]