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Research Project: Genetic and Physiological Mechanisms Underlying Complex Agronomic Traits in Grain Crops

Location: Plant Genetics Research

Title: Transcriptional responses to gibberellin in the maize tassel and control by DELLA domain proteins

item Best, Norman
item DILKES, BRIAN - Purdue University

Submitted to: The Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2022
Publication Date: 10/19/2022
Citation: Best, N.B., Dilkes, B.P. 2022. Transcriptional responses to gibberellin in the maize tassel and control by DELLA domain proteins. The Plant Journal. 112(2):493-517.

Interpretive Summary: During the Green Revolution, reduced height alleles were utilized to improve crop architecture and subsequently improve yields. This was achieved in crop species such as wheat, rice, and barley, but not in maize. The reduced height alleles from wheat, rice, and barley are involved in the signaling pathway of the plant hormone gibberellin. Using these alleles in maize results in additional unwanted traits including increased branching and altered reproductive development and therefore have not been used to improve plant architecture in maize. Our research has identified that the genetic targets in maize that regulate these traits are different. In the current work, we identified a set of candidate genes that could be manipulated in maize to separate their effects on plant height from the deleterious effects on branching and sexual reproductive development. These results will contribute to improved plant architecture in maize by utilizing reduced height alleles involved in gibberellin signaling.

Technical Abstract: The plant hormone gibberellin (GA) impacts plant growth and development differently depending on the developmental context. In the maize (Zea mays) tassel, application of GA alters floral development, resulting in the persistence of pistils. GA signaling is achieved by the GA-dependent turnover of DELLA domain transcription factors, encoded by dwarf8 (d8) and dwarf9 (d9) in maize. The D8-Mpl and D9-1 alleles disrupt GA signaling, resulting in short plants and normal tassel floret development in the presence of excess GA. However, D9-1 mutants are unable to block GA-induced pistil development. Gene expression in developing tassels of D8-Mpl and D9-1 mutants and their wild-type siblings was determined upon excess GA3 and mock treatments. Using GA-sensitive transcripts as reporters of GA signaling, we identified a weak loss of repression under mock conditions in both mutants, with the effect in D9-1 being greater. D9-1 was also less able to repress GA signaling in the presence of excess GA3. We treated a diverse set of maize inbred lines with excess GA3 and measured the phenotypic consequences on multiple aspects of development (e.g., height and pistil persistence in tassel florets). Genotype affected all GA-regulated phenotypes but there was no correlation between any of the GA-affected phenotypes, indicating that the complexity of the relationship between GA and development extends beyond the two-gene epistasis previously demonstrated for GA and brassinosteroid biosynthetic mutants.