Abstract
SummaryCold temperature during the reproductive stage often causes great yield loss of grain crops in subtropical and temperate regions. Previously we showed that the rice transcription factor bZIP73Jap plays an important role in cold adaptation at the seedling stage. Here we further demonstrate that bZIP73Jap also confers cold stress tolerance at the reproductive stage. bZIP73 Jap was up‐regulated under cold treatment and predominately expressed in panicles at the early binucleate and flowering stages. bZIP73Jap forms heterodimers with bZIP71, and co‐expression of bZIP73 Jap and bZIP71 transgenic lines significantly increased seed‐setting rate and grain yield under natural cold stress conditions. bZIP73Jap:bZIP71 not only repressed ABA level in anthers, but also enhanced soluble sugar transport from anthers to pollens and improved pollen grain fertility, seed‐setting rate, and grain yield. Interestingly, bZIP73Jap:bZIP71 also regulated the expression of qLTG3‐1 Nip, and qLTG3‐1 Nip overexpression lines greatly improved rice tolerance to cold stress during the reproductive stage. Therefore, our work establishes a framework for rice cold stress tolerance through the bZIP71‐bZIP73Jap‐qLTG3‐1Nip‐sugar transport pathway. Together with our previous work, our results provide a powerful tool for improving rice cold stress tolerance at both the seedling and the reproductive stages.
Highlights
As rice originated from tropical and subtropical regions, it is vulnerable to cold stress at all growth stages, which is especially critical during the reproductive stage, because it adversely affects grain yield and quality (Espe et al, 2017; Pan et al, 2015; Zhang et al, 2014, 2017)
Together with our previous work, our results provide a powerful tool for improving rice cold stress tolerance at both the seedling and the reproductive stages
We demonstrated that the bZIP71:bZIP73Jap heterodimer plays an important role in rice cold adaptation at the seedling stage (Liu et al, 2018a)
Summary
As rice originated from tropical and subtropical regions, it is vulnerable to cold stress at all growth stages, which is especially critical during the reproductive stage (booting and flowering stage), because it adversely affects grain yield and quality (Espe et al, 2017; Pan et al, 2015; Zhang et al, 2014, 2017). Cold stress may affect pollen germination, pollen tube elongation, fertilization, leading to spikelet sterility (Shinada et al, 2013, 2014). QPSR10 was identified by GWAS using a 1033-accession diversity panel and confers cold tolerance both at the seedling and reproductive stages (Xiao et al, 2018). Little is known about the molecular mechanisms of rice cold tolerance at the reproductive stage
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