Key gene OsBZR4 for regulating embryoless rice traits shows agricultural potential

The development of rice seeds is crucial to determine both the yield of crops and the quality of the grains. Embryo and endosperm – specialized structures for the spread and storage of nutrients, respectively – must develop in a coordinated manner to ensure the viability of the seed.

About 30 years ago, scientists discovered a mutant of embryous rice called EML1. This mutant is precious as a model to study embryo-endosperm interactions and has temperature sensitive features that could be beneficial for reproductive applications. However, the genetic mechanisms responsible for its embryous phenotype have remained clear.

To fill this gap, a research team led by Professor BU Qingyun of the Northeast Institute for Geography and Agroecology of the Chinese Academy of Sciences, identified OSBZR4 as the key regulation gene behind the formation of embryâtus rice and has untied its molecular paths. The results were published in Nature communications July 26.

The study confirms OSBZR4 as a master regulator for the development of embryonic seeds. The genes of the gene sparked embrying seeds in 60% to 100% of plants through several rice cultivars. The analysis of the expression has revealed that OSBZR4 is active specifically at the interface between scutellum (a specialized embryonic structure) and endosperm, where it removes two genes, YUC4 and PIN5B, to control the auxin levels and distribution during early development of the seeds.

Experiences have shown that the exogenous application or overexpression of YUC4 auxin – a gene involved in the synthesis of the auxin – has increased the frequency of embryonic seeds, while the treatment with the transport inhibitor of the n -1 -naphthylphthalamic (NPA) has reduced IT.

In addition, this study explained the sensitivity to the temperature of the mutant. Higher temperatures have strengthened embryles seed rates in BZR4 mutants by activating ospil13, a gene that promotes YUC4 transcription and subsequent accumulation of auxin. This cascade clarifies how the temperature amplifies the embryous line.

In particular, the introduction of the mutant BZR4 allele into elite rice varieties such as ZJ10 and ZJ11 has improved the yield of the strawberry rice and the storableness of the grains – key lines for agricultural productivity.

The targeted manipulation of the OSBZR4 could allow the development of varieties of thermosensitive embrying rice with improved energy reserves and better storability, noted the team.