Key Regulator of Flower Head Development in Rice Discovered

In the 1970s, Chinese scientists figured out how to produce male sterile (MS) rice lines. This allowed breeders to perform controlled pollination for hybrid rice production. However, in these MS lines, the panicle (flower head) often remains enclosed in the leaf sheath, leading to blocked pollination and reduced seed production.

To allow panicles to emerge from the leaf sheath, breeders use rice plants with a mutation in the gene ELONGATED UPPERMOST INTERNODE1 (EUI1), which encodes an enzyme that deactivates the plant hormone gibberellin (GA). This deactivation stimulates panicle extension, as well as increased plant height. Hence, understanding what regulates the enzyme EUI1 in normal wild type plants is crucial.

By isolating and analyzing a dwarf mutant with impaired panicle extension, Dr. Chengcai Chu of the Chinese Academy of Sciences and colleagues uncovered a critical regulator of EUI1 gene expression in rice. This regulator, HOX12, binds directly to regulatory elements of the EUI1 gene, functioning as a transcription factor, or central regulator.

The scientists hypothesize that HOX12 helps regulate plant growth in response to environmental stimuli through its effect on EUI1. The next step will be to determine the initiators of the HOX12-EUI1 system and the conditions under which these occur.

 For more on the study, read the article on Plant Cell.