Abstract
Maize (Zea mays L.) is a cold-sensitive species that often faces chilling stress, which adversely affects growth and reproduction. However, the genetic basis of low-temperature adaptation in maize remains unclear. Here, we demonstrate that natural variation in the type-A Response Regulator 1 (ZmRR1) gene leads to differences in chilling tolerance among maize inbred lines. Association analysis reveals that InDel-35 of ZmRR1, encoding a protein harboring a mitogen-activated protein kinase (MPK) phosphorylation residue, is strongly associated with chilling tolerance. ZmMPK8, a negative regulator of chilling tolerance, interacts with and phosphorylates ZmRR1 at Ser15. The deletion of a 45-bp region of ZmRR1 harboring Ser15 inhibits its degradation via the 26 S proteasome pathway by preventing its phosphorylation by ZmMPK8. Transcriptome analysis indicates that ZmRR1 positively regulates the expression of ZmDREB1 and Cellulose synthase (CesA) genes to enhance chilling tolerance. Our findings thus provide a potential genetic resource for improving chilling tolerance in maize.
Highlights
Maize (Zea mays L.) is a cold-sensitive species that often faces chilling stress, which adversely affects growth and reproduction
To identify novel components involved in chilling tolerance in maize, we screened a population of transgenic maize plants overexpressing >700 maize genes in inbred line LH244 background under cold treatment and identified ZmRR1 (Zea mays Response Regulator 1), which encodes a type-A response regulator
Given that ZmMPK8 negatively regulates the stability of ZmRR1, we examined the expression of ZmDREB1s and ZmCesAs in ZmMPK8-OE and zmmpk[8]
Summary
Maize (Zea mays L.) is a cold-sensitive species that often faces chilling stress, which adversely affects growth and reproduction. We demonstrate that natural variation in the typeA Response Regulator 1 (ZmRR1) gene leads to differences in chilling tolerance among maize inbred lines. The activation of cold signal transduction and downstream responsive events relies on phosphorylation mediated by protein kinases[18]. (OST1)/SNF1-related protein kinase 2.6) phosphorylates ICE1 (Inducer of CBF expression 1), which activates DREB1 gene transcription and triggers the cold stress response in Arabidopsis thaliana[19,20,21]. Cold-responsive protein kinase 1 (CRPK1) phosphorylates 14-3-3 proteins, which import from the cytoplasm into the nucleus and destabilize DREB1 proteins to negatively regulate Arabidopsis freezing tolerance[22]. The mitogen-activated protein kinases MPK3/6 regulate the cold response by phosphorylating and modulating the stability of ICE123,24. The mechanism by which type-A RRs regulate cold stress and type-A RRs is regulated under cold stress in crops remain elusive
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