The role of SPY and its TPR domain in the regulation of gibberellin actionthroughout the life cycle of Petunia hybrida plants

Izhaki, A Swain, SM Tseng, TS Borochov, A Olszewski, NE Weiss, D

A. Izhaki et al., The role of SPY and its TPR domain in the regulation of gibberellin actionthroughout the life cycle of Petunia hybrida plants, PLANT J, 28(2), 2001, pp. 181-190

37

INGLESE

Article

Plant Sciences","Animal & Plant Sciences

PLANT JOURNAL

0960-7412 → ACNP

28

2

2001

181 - 190

ISI

0960-7412(200110)28:2<181:TROSAI>2.0.ZU;2-5

SPY acts as a negative regulator of gibberellin (GA) action in Arabidopsis, but its mode of action and regulation are still unknown. SPY over-expressi on in transgenic petunia plants affected various GA-regulated processes, in cluding seed germination, shoot elongation, flower initiation, flower devel opment and the expression of a GA-induced gene, GIP, A similar phenotype wa s obtained when wild-type petunia plants were treated with the GA-biosynthe sis inhibitor, paclobutrazol. The N-terminus of SPY contains tetratricopept ide repeats (TPR). TPR motifs participate in protein-protein interactions, suggesting that SPY is part of a multiprotein complex. To test this hypothe sis, we over-expressed the SPY's TPR region without the catalytic domain in transgenic petunia and generated a dominant-negative SPY mutant. The trans genic seeds were able to germinate on paclobutrazol, suggesting an enhanced GA signal. We cloned the petunia SPY homologue, PhSPY, and showed that its mRNA level is not affected by GA or ABA. The results of this study support the role of SPY as a negative regulator of GA action, suggest that the TPR domain is required for the interaction with other proteins to form an acti ve complex and indicate that different plants use similar mechanisms to tra nsduce the GA signal.