ZTL regulates thermomorphogenesis through TOC1 and PRR5

Abstract

Plants adapt to high temperature stresses through thermomorphogenesis, a process that includes stem elongation and hyponastic leaf growth. Thermomorphogenesis is gated by the circadian clock through two evening-expressed clock components, TIMING OF CAB EXPRESSION1 (TOC1) and PSEUDO-RESPONSE REGULA-TORS5 (PRR5). These proteins directly interact with and inhibit PHYTOCHROME INTERACTING FACTOR4 (PIF4), a basic helix-loop-helix transcription factor that promotes thermoresponsive growth. PIF4-mediated thermoresponsive growth is positively regulated by ZEITLUPE (ZTL), a central clock component, but the molecular mechanisms underlying this are poorly understood. Here, we show that ZTL regulates thermoresponsive growth through TOC1 and PRR5. Genetic analyses reveal that ZTL regulates PIF4 activity as well as PIF4 expression. In Arabidopsis thaliana, ztl mutants exhibit highly accumulated TOC1 and PRR5 and unresponsive expression of PIF4 target genes under exposure to high temperatures. Mutations in TOC1 and PRR5 restore thermoactivation of PIF4 target genes and thermoresponsive growth in ztl mutants. We also show that the molecular chaperone heat-shock protein 90 promotes thermoresponsive growth through the ZTL-TOC1/PRR5 signaling module. Further, we show that ZTL protein stability is increased at high temperatures. Taken together, our results demonstrate that ZTL-mediated degradation of TOC1 and PRR5 enhances the sensitivity of hypocotyl growth to high temperatures.

GmCOL4-GmZTL1 interaction co-regulates GmSBH1 to improve seed deterioration under high temperature and humidity stress and affect leaf growth and development

“…5b). Additionally, COL and ZTL was shown to function not only in the circadian clock but in heat stress (Wang et al, 2013b, Gil et al, 2017, Huang et al, 2022, Seo et al, 2023. Herein, GmCOL4 and GmZTL1 were found both to be strongly induced by HTH stress in developing seeds of soybean (Fig.…”

Comparative proteomics in tall fescue to reveal underlying mechanisms for improving Photosystem II thermotolerance during heat stress memory

“…Evidence from triple uch mutants of Arabidopsis demonstrate elongated circadian clock periods with increased TOC1(TIMING OF CAB EXPRESSION1) and GI (GIGANTEA) transcripts at 29 ℃ [ 89 ]. At 28 ℃, TOC1 undergoes degradation by ZTL (ZEITLUPE), facilitating thermomorphogenesis [ 90 ]. Significantly, ZTL, defined as an F-box E3 ubiquitin ligase, ensures protein quality control and maintains the stability of the circadian clock under heat stress (HS), with the aid of co-chaperone protein HSP90 and GI [ 91 ].…”

The Roles of Circadian Clock Genes in Plant Temperature Stress Responses

“…ZTL increases thermotolerance through a protein expression system [10]. In contrast to thermomorphogenesis, ZTL appears to regulate different high-temperature responses through distinct mechanisms; the thermotolerance defect in ztl mutants is not restored by TOC1 and PRR5 mutations [85]. Increased ZTL expression at high temperatures may promote plant survival under high-temperature stress.…”