Biotech Updates

Positional Cloning of Cold Tolerance Trait in Rice

June 4, 2010

Rice yields are low in areas of low temperature. Previous studies have revealed that cold-induced male sterility (CIMS) often occur during the booting stage. A follow-up study was conducted by Koji Saito of National Agricultural Research Center for Hokkaido Region together with other scientists to further map the location of cold tolerance trait (Ctb1). They conducted a map-based cloning of Ctb1 which is composed of two genes that code for an F-box protein and a ser/thr protein kinase.

The F-box protein was usually expressed in young panicles, while the ser/thr protein kinase gene was evident in the leaves and immature panicles. These two genes were cloned from a cold-tolerant variety, and introduced into a cold-sensitive variety, and a cold-sensitive line. The cold tolerance of the clones exposed to low temperature was measured by the degree of spikelet fertility. The findings proved that F-box gene is responsible for cold tolerance. Cold tolerance correlate with longer anther, and the transgenic plants had greater anther length compared to unmodified controls. The F-box protein interacts with Skp1, a subunit of E3 ubiquitin ligase, which may imply a relationship between ubiquitin–proteasome pathway and cold tolerance at the booting stage.

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