GW5

A major QTL on chromosome 5, qGW5, which is associated with reduced grain width not only in the isogenic Asominori background but also in the recombinant background of Asominori and IR24 under multiple environmental conditions

Annotated Information

Mutation

GW5 is associated with a 1 212-bp deletion in the Asominori cultivar For genetic analysis and isolation of the dominant narrow-grain QTL, named GW5, the F2 population was constructed from a cross between Asominori and CSSL28, and the QTL was dissected into a single gene . By means of linkage analysis using the genotype data of both the GW5 gene and simple sequence repeat (SSR) markers, the GW5 gene was mapped to an interval between markers RM3328 and RMw513 in 805 homozygotes . Thus, the GW5 gene was mapped to a genomic region 2.7 cM in length, located 2.3 cM from RM3328 and 0.37 cM from RMw513. In this region, three bacterial artificial chromosome (BAC) contigs were found – OJ1725_E07, OJ1097_A12 and B1007D10

Function

1.Stability of QTL for rice grain width and gene actionof identified QTL. The observed stability and gene action of these QTL indicates that qGW-5 is the most important genetic factor that controls rice grain width difference between the Asominori and IR24 parental lines. 2.GW5 physically interacts with polyubiquitin Sequence analysis indicated that GW5 encodes a novel protein without significant homology to any proteins of known biochemical function. The protein is predicted to contain an NLS and an arginine-rich domain. Transient expression in onion epidermal cells showed that the GW5-GFP fusion protein is exclusively localized to the Nucleus. In an effort to identify the functional partners of GW5, polyubiquitin protein interacts with GW5. This result was found 14 times in about 200 candidate positive clones on synthetic growth medium without leucine, tryptophan, histidine and adenine. X-gal filter lift assays also detected a clear interaction between GW5 and polyubiquitin . This suggests that the GW5 protein may play an important role in regulating the grain shape through involvement with the ubiquitin-proteasome pathway.

Expression

GW5 is expressed in slender-grain rice. The sequence of 9 311 (a narrow-grain indica rice cultivar) in the cognate region is similar to that in the GW5 region in CSSL28. Analysis of the indica rice genome sequence showed that GW5 represents a single copy gene without any expressed sequence tags (ESTs) or cDNA support. However, the expression of the candidate ORF was detected in the tiling microarray database of 9 311 (GenBank Acc: CL971152) To further confirm the expression of GW5, RT-PCR analysis were confirmed by sequencing analyses. Therefore, GW5 is expressed in CSSL28.

Labs working on this gene

National Key Laboratory for Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University,

References

1.Jianfeng Weng etc. Isolation and initial characterization of GW5, a major QTL associated with rice grain width and weight. Cell Research, 2008, 18(12): 1199-1209

2.Xiangyuan Wan etc. Quantitative Trait Loci (QTL) Analysis For Rice Grain Width and Fine Mapping of an Identified QTL Allele gw-5 in a Recombination Hotspot Region on Chromosome 5 .Genetics, 2008, 179(4): 2239-2252

3.X. Y. Wan etc. Stability of QTLs for rice grain dimension and endosperm chalkiness characteristics across eight environments. Theoretical and Applied Genetics, 2005, 110(7): 1334-1346