Abnormally developed endosperm strongly affects rice appearance and grain
weight. Endosperm formation is a complex process, but several factors remain
largely unknown. Scientists from the China National Rice Research Institute
studied a recessive mutant, wb1, in hopes of studying factors affecting
endosperm development in rice.

The wb1 mutant develops a white-belly endosperm and abnormal starch granules
in the inner portion of white grains. Grains of wb1 also showed higher grain
chalkiness and a lower 1000-grain weight, a 34% decrease from that of
wildtype grains. The contents of amylose and amylopectin in wb1
significantly decreased, and its physical properties were also altered.

The analysis identified 12 candidate genes that could be implicated for the
wb1 mutant. Further analysis of transcript levels of all candidate genes
showed that White Belly 1 (WB1), which encodes a cell-wall invertase, was
the most probable cause of white-belly endosperm phenotype.



Switching off of WB1 using the CRIPR-Cas9 system in Nipponbare rice lines
confirms that WB1 regulates endosperm development and is responsible for the
wb1 mutation.





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