Abstract
Heading date and panicle architecture are important agronomic traits in rice. Here, we identified a gene MOTHER OF FT AND TFL1 (OsMFT1) that regulates rice heading and panicle architecture. Overexpressing OsMFT1 delayed heading date by over 7 d and greatly increased spikelets per panicle and the number of branches. In contrast, OsMFT1 knockout mutants had an advanced heading date and reduced spikelets per panicle. Overexpression of OsMFT1 significantly suppressed Ehd1 expression, and Ghd7 up-regulated OsMFT1 expression. Double mutants showed that OsMFT1 acted downstream of Ghd7. In addition, transcription factor OsLFL1 was verified to directly bind to the promoter of OsMFT1 via an RY motif and activate the expression of OsMFT1 in vivo and in vitro. RNA-seq and RNA in situ hybridization analysis confirmed that OsMFT1 repressed expression of FZP and five SEPALLATA-like genes, indicating that the transition from branch meristem to spikelet meristem was delayed and thus more panicle branches were produced. Therefore, OsMFT1 is a suppressor of flowering acting downstream of Ghd7 and upstream of Ehd1, and a positive regulator of panicle architecture.
Highlights
Heading date in rice (Oryza sativa) is crucial for plants to adapt to the growing environment and for the improvement of yield potential
A slight but significant promotion in heading date and decrease of spikelets per panicle were observed in all OsMFT1 knockout mutants compared with wild type (WT) (Fig. 1F, I).The number of primary branches and secondary branches was significantly reduced (Fig. 1J).Taken together, OsMFT1 is a suppressor of heading and positive regulator of spikelets per panicle in rice
Previous studies indicated that FLOWERING LOCUS T (FT)-like genes generally induce flowering both in monocots and dicots, while TERMINAL FLOWER1 (TFL1)-like genes delay flowering and regulate the inflorescence architecture, including TFL1 in Arabidopsis, RCNs in rice, and ZCNs in maize (Alvarez et al, 1992; Nakagawa et al, 2002;Zhang et al.,2005;Danilevskaya et al.,2010;Wickland and Hanzawa, 2015).As the evolutionary ancestor of FT and TFL1, MOTHER OF FT AND TFL1 (MFT)-like genes are generally related to seed germination (Xi et al, 2010; Nakamura et al, 2011; Li et al, 2014; Hu et al, 2016)
Summary
Heading date (flowering time) in rice (Oryza sativa) is crucial for plants to adapt to the growing environment and for the improvement of yield potential. It is determined by the interaction of endogenous signals and environmental factors. Florigen is a key endogenous signal that is synthesized in the leaves and moves to the shoot apex to induce flowering. Many environmental factors could induce or suppress florigen expression. Photoperiod (day length) is the most important environmental factor affecting flowering time (Song et al., 2015). Many genes have been identified as involved in the photoperiod-mediated flowering pathway.
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