Phytochrome B regulates Heading date 1 (Hd1)-mediated expression of rice florigen Hd3a and critical day length in rice

• Published in: Molecular genetics and genomics : MGG Vol. 285; no. 6; pp. 461 - 470
• Main Authors: Ishikawa, Ryo, Aoki, Mayumi, Kurotani, Ken-ichi, Yokoi, Shuji, Shinomura, Tomoko, Takano, Makoto, Shimamoto, Ko
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.06.2011; Springer Nature B.V
• Subjects: Animal Genetics and Genomics; Arabidopsis; Biochemistry; Biomedical and Life Sciences; Circadian Rhythm; Flowers; Gene Expression Regulation, Plant; Genomics; Human Genetics; Life Sciences; Light; Microbial Genetics and Genomics; Original Paper; Oryza - physiology; Oryza sativa; Photoperiod; Phytochrome B - physiology; Plant Genetics and Genomics; Plant Proteins - physiology; Proteins; Japan; Flowering; Photoperiod; Florigen; Phytochrome B
• ISSN: 1617-4615; 1617-4623
• DOI: 10.1007/s00438-011-0621-4

Many plants require circadian clock and light information for the photoperiodic control of flowering. In Arabidopsis , a long-day plant (LDP), flowering is triggered by the circadian clock-controlled expression of CONSTANS ( CO ) and light stabilization of the CO protein to induce FT ( FLOWERING LOCUS T ). In rice, a short-day plant (SDP), the CO ortholog Heading date 1 ( Hd1 ) regulates FT ortholog Hd3a , but regulation of Hd3a by Hd1 differs from that in Arabidopsis . Here, we report that phytochrome B (phyB)-mediated suppression of Hd3a is a primary cause of long-day suppression of flowering in rice, based on the three complementary discoveries. First, overexpression of Hd1 causes a delay in flowering under SD conditions and this effect requires phyB, suggesting that light modulates Hd1 control of Hd3a transcription. Second, a single extension of day length decreases Hd3a expression proportionately with the length of daylight. Third, Hd1 protein levels in Hd1 -overexpressing plants are not altered in the presence of light. These results also suggest that phyB-mediated suppression of Hd3a expression is a component of the molecular mechanism for critical day length in rice.