The numbers of grain-bearing branches ('tillers') per plant are increased in
GRVs, further enhanced by increased nitrogen fertilizer use to boost grain
yield. However, fertilizers are costly to farmers and cause extensive
environmental damage. The study led by Professor Xiangdong Fu from the
Chinese Academy of Sciences' Institute of Genetics and Developmental
Biology, and Professor Nicholas Harberd from the Department of Plant
Sciences at the University of Oxford has for the first time discovered a
gene that can help reach that goal.

The study has identified a rice gene that responds to nitrogen, increasing
the accumulation in plant cells of a protein called NGR5.
Nitrogen-stimulated NGR5 accumulation then alters the structure of genes
that inhibit tiller growth, switching them off and thus increasing the
numbers of yield-enhancing tillers. Increased tiller number is also caused
by DELLA, another branching-promoting protein, whose accumulation is reduced
by the hormone gibberellin (GA). The study found that GA also reduces NGR5
accumulation, and that tiller growth is the product of complex interactions
between the NGR5 and DELLA proteins.

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