The role of Phytochrome-Interacting Factor 3 in regulating growth and development in hexaploid wheat

Abstract

The development of chloroplasts requires tight control to prevent the accumulation of reactive oxygen species and seedling damage. Work with Arabidopsis indicates that gibberellin signalling plays an important role in photo-oxidative stress responses through targeted degradation of growth repressing DELLA proteins. In wheat, mutants of the DELLA protein RHT-1 were the basis of the semi-dwarf lines so crucial to the Green Revolution. These mutants, however, display adverse pleiotropic effects impacting on wheat physiology. Elucidating the downstream targets of RHT-1 could therefore provide a mechanism for targeting specific RHT-1 functions without off-target consequences. In Arabidopsis, one mechanism by which DELLAs function is through repressing the activity of the Phytochrome Interacting Factors (PIFs). PIFs are transcription factors that repress light responses in plants, leading to the promotion of growth and repression of chloroplast development.

To determine the role of PIFs in regulating growth and chloroplast development in wheat we have searched the bread wheat genome for orthologues of known Arabidopsis and rice PIF genes. Annotation of wheat PIF gene sequences has been achieved through analysis of RNA-seq data and a specific PIF3 orthologue has been identified. A range of approaches have been used to manipulate TaPIF3 levels in order to study its function. Potential loss-of-function mutations in each of the three TaPIF3 homoeologues have been identified by TILLING and stacked to generate a TaPIF3 mutant. A wheat TaPIF3 overexpression line has also been generated. Phenotypic analysis of the TaPIF3 triple mutant and overexpression lines indicate a role for TaPIF3 in the regulation of stem elongation and ear length. These results suggest that TaPIF3 is a promising target for downstream regulation of wheat physiology. Furthermore, a heterologous complementation approach has been used to further characterise the function of TaPIF3.

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ORCID for Matthew Terry: orcid.org/0000-0001-5002-2708

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