OsHDT1 over-expression induces early flowering in the hybrid.

(A). Comparison of OsHDT1 transcript accumulation in transgenic and wild type (WT) parent MH63 and hybrid SY63 by semi-quantitative (22 cycles) RT-PCR. Three independent over-expression (OX) positive (+, lines 5, 8, and 9) or negative (−, lines 29, 30 and 31) and RNAi positive (+, line 1, 8 and 9) and negative (−, lines 6, 14 and 15) transgenic lines in both MH63 and SY63 backgrounds were analyzed. Rice actin transcripts were detected as controls. (B). OsHDT1 protein levels in RNAi (line 1), over-expression (OX, line 5) and wild type MH63 (MH) and SY63 (SY) detected by Western blots using anti-OsHDT1. RNAi plants in MH63 and SY63 were designated as PR and FR, respectively; Over-expression plants in MH63 and SY63 were designated as PU and FU, respectively. (C). Over-expression of OsHDT1 induces an early heading flowering phenotype in SY63 background. a, comparison between MH63 and PU (line 5) at 98 days after sowing. b, comparison between SY63 and FU (line 5) taken at 88 days after sowing. (D). Heading dates of transgenic positive and negative lines in MH63 and SY63 backgrounds in comparison with the respective wild type lines under natural long day conditions. The transgenic lines used are indicated at the bottom. Asterisks indicate ranking by LSD test at highly significant (*P<0.01) differences relative to the corresponding wild type plants.