Abstract
Dark-adapted rice leaves were illuminated at PPFD = 1,500 μmol m-2 s-1 for five minutes, and NPQ size after the treatment was measured. Sasanishiki (Japonica cv.) showed NPQ size of around 2.0, whereas Habataki (Indica cv.) was around 1.5. We also measured around 50 cv.s of World Rice Core Collection, of which Japonica cv.s showed NPQ larger than 1.65 and Indica cv.s showed NPQ smaller than 1.65, except two cv.s. We then did QTL analysis between Sasanishiki and Habataki using backcross inbred lines. Tow QTLs qNPQ1-1 and qNPQ1-2, which regulate NPQ size, were identified on the chromosome 1. Of these two loci qNPQ1-2 had larger additive effect, and Sasanishiki allele of qNPQ1-2 positively regulates NPQ size. PsbS1, one of the two PsbS homologs, lies within qNPQ1-2 region, suggesting the possibility that PsbS is involved in the difference of NPQ size between Sasanishiki and Habataki. When we observed the relationship between PsbS1 expression levels and NPQ sizes in PsbS1 overexpressors, NPQ sizes were positively correlated with PsbS1 expression levels. Compared with the DNA sequence of Japonica cultivars, Indica cultivars had a 2.7-kb deletion at 0.4-kb upstream of PsbS1 gene.
