TaGAST1, One of Wheat Gast Family of Small Polypeptides, Interacts with TaCypA1 during Spike Development.

Gibberellic acids (GAs) are influential plant hormones that function during a plant’s whole lifetime. GAs regulate major growth and developmental processes such as seed germination, stem elongation, flowering, and fruit development. Among numerous GA-responsive genes, the GAST family are known to be important growth inducers and regulators of development that act in response to GA. In this study, four GA-stimulated genes were isolated from wheat and designated TaGAST1, 2, 3, and 4 (Triticum aestivum gibberellic acid stimulated transcript 1, 2, 3 and 4). All TaGAST family members encode approximately 100 amino acid residues and include highly conserved cysteine-rich domains termed GASA domains in their C-terminal regions, along with divergent intermediate N-terminal regions. The expression of the TaGASTs was analyzed at the inflorescence development stage, in different tissues, and under the application of phytohormones. TaGAST1 was prominently expressed at the inflorescence development stage in response to phytohormone treatment. However, TaGAST1 was not expressed in the seedlings except under abscisic acid (ABA) treatment. TaGAST2 and TaGAST3 showed moderate expression in the spike but vigorous transcript accumulation in the seedling. TaGAST4 was predominantly expressed only in the seedling. To identify putative interacting proteins of the TaGAST genes during spike development, a yeast two-hybrid assay was conducted and wheat cyclophilin A-1 (TaCypA1) was identified as a TaGAST1 interacting protein. The expression pattern of TaCypA1 in the developing spike was opposite to that of TaGAST1. A bimolecular fluorescence complementation assay revealed that the interaction of TaGAST1 with TaCypA1 is targeted to the plasma membrane.

Aknowledgement: This work was carried out with the support of the Next-Generation BioGreen21 Program for Agriculture & Technology Development (Project No. PJ01103501), Rural Development Administration, Republic of Korea. This work was also supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP) (NRF-2014R1A1A1003621)