Three annotated genes (LOC_Os02g47280, LOC_Os02g47290 and LOC_Os02g47300) were identified within the critical 33.2-kb genomic region of Nipponbare (japonica) genome (http://rice.plantbiology.msu.edu/). LOC_Os02g47290 and LOC_Os02g47300 encoded hypothetical
selleck proteins with no gene ontology annotation; thus those two genes might have no or marginal direct relevance to the grain shape development according to their putative functions. The LOC_Os02g47280 encodes a growth-regulating factor protein, which belongs to the GRF family of proteins consisting of twelve members. The protein of LOC_Os02g47280 has two putative alternative splice forms, and both contain a WRC domain and a QLQ domain. Interestingly, the protein of LOC_Os02g47280 shares homology with a protein in Brachypodium, Zea mays L., Populus L. and Sorghum vulgare Pers.
(http://rice.plantbiology.msu.edu/). The WRC domain contains a putative nuclear localization signal and a zinc-finger motif (C3H). The WRC domain was suggested to be involved in DNA binding while QLQ domain was shown to affect protein–protein interactions [17]. Recently it was demonstrated that LOC_Os02g47280 is down-regulated by miR396 during grain development in rice [18]. Therefore, LOC_Os02g47280 should be considered the most likely candidate for GS2. We are currently investigating EGFR inhibitor a genetic complementation of the candidate gene by transformation and other functional analyses. To date, more than 40 QTLs related to grain shape and yield have been primarily mapped on chromosome 2 of rice (http://www.gramene.org/). Some of these are located Aspartate in the proximity of GS2. For example, the QTL qGL-2a,
which affects grain length, was mapped in an interval between the restriction fragment length polymorphism (RFLP) marker C560 and C1408, accounting for 11.7% of total phenotypic variations [19]. Another QTL qGL-2 responsible for grain length was detected between the RFLP marker C601and R3393 using chromosome segment substitution line (CSSL) populations across eight environments [20]. Of note, the QTL associated with grain number, gpl2.1, was detected at the end of the long arm of chromosome 2 using an IR64/O. rufipogon BC2F2 population [21]. However the QTL gpl2.1 explained only 4.8% of phenotypic variations. In addition, four QTLs controlling grain shape and yield have been cloned on chromosome 2: qGY2–1 [22], GW2 [6], LP [23] and PGL2 [24]. Precisely, GW2, a major QTL of grain width and weight, was mapped to a 8.2-kb interval flanked by markers W024 and W004 with a set of near-isogenic lines (NILs, BC2F2/BC3F2/BC3F4) developed from a sub-specific cross of the japonica cultivar Wy3 and indica cultivar FAZ1 [6]. The LARGER PANICLE (LP) gene encodes a Kelch repeat-containing F-box protein and plays an important role in regulating plant architecture, particularly panicle architecture.