EXAMINING THE FUNCTION OF GID1-REGULATED GENES
Ge, W.J.1 and Steber, C.M.2
1State Key Laboratory of Grassland Agro-ecosystems, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, China
2United States Department of Agriculture-Agricultural Research Service and Department of Crop and Soil Science, Washington State University, Pullman, Washington, USA
Contact: Wenjing Ge, firstname.lastname@example.org
Plant species survival and agriculture both depend on seed germination occurring in a season and environment conducive to seedling growth and development. Dormant seeds are unable to germinate when first released from the mother, thereby preventing germination out of season (fall vs spring). Dormancy can be lost through a period of dry storage called after-ripening (AR), or exposure to the moist wintry condition of cold imbibitions. The plant hormone gibberellin (GA) stimulates seed germination. The proposed research examines the hypothesis that gibberellin A (GA) hormone receptors regulate dormancy loss via regulation of gene transcription and translation. GA signaling leads to inactivation or destruction of DELLA (Asp-Glu-Leu-Leu-Ala) family repressors of GA responses. In Arabidopsis, GA is perceived by the three homologous receptors, GID1a, GID1b, and GID1c (GA-INSENSITIVE DWARF1, 68-85% amino acid identity) comprised of a GA-binding core connected to a lid domain by an a-loop hinge.
In sly1 (sleepy1) mutants, GA and GID1 can also inactivate DELLA repressors via GID1-GA-DELLA complex formation without DELLA proteolysis. This is seen when GA-insensitive sly1-2 seed dormancy is rescued without DELLA destruction by long after-ripening (2 years AR, 85% germination) and GID1b overexpression (GID1b-OE, 75%). If AR and GID1b-OE reduce sly1-2 seed dormancy via similar mechanisms, then they should result in similar transcriptome changes.
Nelson and Steber identified transcripts showing altered accumulation when germination of the GA-insensitive sly1-2 mutant was rescued by after-ripening or by GID1b-OE. And stimulation of sly1-2 germination by AR and GID1b-OE are associated with partly overlapping transcriptional changes. This suggests that these 26 genes showing differential regulation by GID1b-OE are important regulators of dormancy. Thus, we will determine whether genes regulated in response to GID1b-OE play an important role in seed dormancy.
So far, we have been working on determining if GID1b-OE-regulated transcripts are differentially expressed in gid1 loss of function mutants. The effects of GID1 loss and gain-of-function on the expression of GID1b-OE-regulated genes will be examined in dormant (0 wk AR) and after-ripened (1 mo AR) seeds by RT-qPCR analysis performed at the different imbibition time points used for the microarray analysis.