Os07g0505200

The rice Os07g0505200 was reported as OsSPL13. OsSPL13 belongs to the SQUAMOSA PROMOTER BINDING PROTEIN (SBP) family of transcription factors.

Annotated Information

Function

• OsSPL13 gene locates on the a major quantitative trait locus, GLW7, and encodes the plant-specific transcription factor OsSPL13, positively regulates cell size in the grain hull, resulting in enhanced rice grain length and yield, but does not regulate grain width.OsSPL13 has an important role in the accumulation of dry matter in rice grains.OsSPL13 regulates grain shape through activation of cell size regulation machinery.
• A tandem-repeat sequence in the 5′ UTR of OsSPL13 alters its expression by affecting transcription and translation and that high expression of OsSPL13 is associated with large grains in tropical japonica rice.
• OsSPL13 is one of the targets of OsmiR156.OsSPL13 directly targets SRS5, and functions as a positive regulator of SRS5 expression in the regulation of hull cell size in rice.

Mutation

• Scientists carried out RNA interference (RNAi) to suppress the expression of OsSPL13 in the small-grain japonica variety Dongjing and the large-grain japonica variety GP579. The corresponding transgenic plants showed significantly decreased 1,000-grain weight, grain length and grain thickness when compared with the wild-type plants. No changes were detected in grain width (Fig. 3a,b,d,e). Control plants with pTCK303 did not show any differences in grain shape for the transgenic plants.

Figure 1. Analyses of grain shape for wild-type Dongjing, transgenic plants and a T-DNA mutant .

Expression Pattern

According to rice spikelet developmental stages29, OsSPL13 was detected when the primary- and secondary branch primordia initiated (Fig. 6a–c) and was strongly expressed in floral organ primordia (Fig. 6d). OsSPL13 was highly expressed in the middle of the lemma and palea when florets were about 1 mm in length (Fig. 6e), and expression gradually decreased during the growth of the florets and stamen (Fig. 6f). When florets reached 2.2 mm in length, only weak OsSPL13 expression was detected in the hulls of the florets (Fig. 6g). Interestingly, OsSPL13 expression was strong in the apices of the lemma and palea when the hulls were 4–5 mm in length and gradually decreased from apices to the middle of the hull (Fig. 6h–j). No signal was detected in the negative control (Fig. 6k).

Figure 1. In situ hybridization for OsSPL13 in primary branch formation .

Evolution

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Labs working on this gene

• National Center for Gene Research, Chinese Academy of Sciences Center for Excellence of Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
• State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, China.
• Crop Biotech Institute, Kyung Hee University, Yongin, Republic of Korea. Correspondence should be addressed to B.H.