Abstract
BackgroundAppropriate flowering time is very important to the success of modern agriculture. Maize (Zea mays L.) is a major cereal crop, originated in tropical areas, with photoperiod sensitivity. Which is an important obstacle to the utilization of tropical/subtropical germplasm resources in temperate regions. However, the study on the regulation mechanism of photoperiod sensitivity of maize is still in the early stage. Although it has been previously reported that ZmCCT is involved in the photoperiod response and delays maize flowering time under long-day conditions, the underlying mechanism remains unclear.ResultsHere, we showed that ZmCCT overexpression delays flowering time and confers maize drought tolerance under LD conditions. Implementing the Gal4-LexA/UAS system identified that ZmCCT has a transcriptional inhibitory activity, while the yeast system showed that ZmCCT has a transcriptional activation activity. DAP-Seq analysis and EMSA indicated that ZmCCT mainly binds to promoters containing the novel motifs CAAAAATC and AAATGGTC. DAP-Seq and RNA-Seq analysis showed that ZmCCT could directly repress the expression of ZmPRR5 and ZmCOL9, and promote the expression of ZmRVE6 to delay flowering under long-day conditions. Moreover, we also demonstrated that ZmCCT directly binds to the promoters of ZmHY5, ZmMPK3, ZmVOZ1 and ZmARR16 and promotes the expression of ZmHY5 and ZmMPK3, but represses ZmVOZ1 and ZmARR16 to enhance stress resistance. Additionally, ZmCCT regulates a set of genes associated with plant development.ConclusionsZmCCT has dual functions in regulating maize flowering time and stress response under LD conditions. ZmCCT negatively regulates flowering time and enhances maize drought tolerance under LD conditions. ZmCCT represses most flowering time genes to delay flowering while promotes most stress response genes to enhance stress tolerance. Our data contribute to a comprehensive understanding of the regulatory mechanism of ZmCCT in controlling maize flowering time and stress response.
Highlights
Appropriate flowering time is very important to the success of modern agriculture
Shi et al [15] showed that ZmCCA1a is likely to be an important component of the circadian clock in maize, and flowering time was delayed in the ZmCCA1a-overexpressing A. thaliana lines under long days (LD) conditions
ZmNF-YA3 encodes an NF-YA subunit in maize, and the zmnf-ya3 mutant showed delayed flowering under LD conditions, whereas there was no significant difference in flowering time compared to the wild type (WT) under short days (SD) conditions [19]
Summary
Appropriate flowering time is very important to the success of modern agriculture. Maize (Zea mays L.) is a major cereal crop, originated in tropical areas, with photoperiod sensitivity. It has been previously reported that ZmCCTis involved in the photoperiod response and delays maize flowering time under long-day conditions, the underlying mechanism remains unclear. CCT domain genes play an important role in flowering time regulation in maize [4]. A Harbinger-like transposable element that tropical SD maize germplasms do not have, acts in cis to promote flowering under LD conditions by repressing the expression of ZmCCT9 [7]. Under LD conditions, ZmCCT9 delays flowering time by negative regulation of the florigen gene ZCN8 [7]. Shi et al [15] showed that ZmCCA1a is likely to be an important component of the circadian clock in maize, and flowering time was delayed in the ZmCCA1a-overexpressing A. thaliana lines under LD conditions. ZmNF-YA3 encodes an NF-YA subunit in maize, and the zmnf-ya mutant showed delayed flowering under LD conditions, whereas there was no significant difference in flowering time compared to the WT under SD conditions [19]
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