Abstract
Alleles of rice Dense panicle 1 (Dn1) mutant, which is semi-dwarf and increases spikelet number per plant, were compared. Based on their nucleotide sequences, DN1-1 was presumed to be a truncated protein which lacked most of cysteine-rich region in the C-terminus, and Dn1-3 was predicted to encode only the coiled-coil domain and a NLS. The expression level in shoot apical meristem and/or root tip was two or three times higher in Dn1-1 plant, and more than ten times higher in Dn1-3 plant than wild type. Since expression of DN1, DN1-1, and DN1-3 was driven by the same endogenous promoter, the wild-type mRNA was implied to be more degraded than that of the mutants. In the Nipponbare background, both Dn1-1 and Dn1-3 were semi-dwarf, but only Dn1-1 increased spikelet number.
Using transgenics which overexpressed fusion protein of GFP and DN1, it was clarified that at least DN1-1 contains transmembrane domain and that ca. 4 kDa N-terminus fragment was cleaved and released into the cytoplasm in both wild type and Dn1-1 plants.
Introgression of Dn1-1 allele in different backgrounds by backcrossing revealed that the timing of the effect of this allele depended on the genetic background.
