Map-based cloning of a spotted-leaf mutant gene OsSL5 in Japonica rice

A japonica rice mutant, spotted-leaf 5 (sl5), was identified from YUN32 by EMS mutagenesis. The number of spots in leaves increased from maturity to late maturity in sl5, however, the leaves did not dry and withered. The sl5 mutant exhibited significantly lower height, spike length, primary branch number, second branch number, and 1,000-grain weight than YUN32. Genetic analysis shows that sl5 is controlled by a single recessive gene. OsSL5 was mapped into a 40-kb interval flanked by markers MX4 and MX5 on chromosome 7 by map-based cloning. Four ORFs, including one SPL5 gene, were identified in this region. Sequencing reveals that the G base at site 3,647 of the OsSL5 coding region was changed to A. The mutant OsSL5 site was different from that of the SPL5 mutant, with the background of indica rice. OsSL5 is thus a new SPL5 allele which encodes a putative splicing factor 3b subunit 3. QPCR shows that OsSL5 expression in the sl5 mutant is significantly lower than that in YUN32. The spotted leaf-related genes RLIN1, SPL28, and SPL18 expressions were significantly decreased, whereas the SPL7 and SL gene expressions significantly increased. The OsSL5 gene may be important for rice cell apoptosis regulation.