Blue Light- and Low Temperature-Regulated COR27 and COR28 Play Roles in the Arabidopsis Circadian Clock

Abstract

Light and temperature are two key environmental signals that profoundly affect plant growth and development, but underlying molecular mechanisms of how light and temperature signals affect the circadian clock are largely unknown. Here, we report that COR27 and COR28 are regulated not only by low temperatures but also by light signals. COR27 and COR28 are negative regulators of freezing tolerance but positive regulators of flowering, possibly representing a trade-off between freezing tolerance and flowering. Furthermore, loss-of-function mutations in COR27 and COR28 result in period lengthening of various circadian output rhythms and affect central clock gene expression. Also, the cor27 cor28 double mutation affects the pace of the circadian clock. Additionally, COR27 and COR28 are direct targets of CCA1, which represses their transcription via chromatin binding. Finally, we report that COR27 and COR28 bind to the chromatin of TOC1 and PRR5 to repress their transcription, suggesting that their effects on rhythms are in part due to their regulation of TOC1 and PRR5. These data demonstrate that blue light and low temperature-regulated COR27 and COR28 regulate the circadian clock as well as freezing tolerance and flowering time.

Circadian diversity in SwedishArabidopsisaccessions is associated with naturally occurring genetic variation inCOR28

“…Analysis of the DF rhythms confirmed that periods in cor28 mutants ( cor28-1 =25.3h, SD=1.73; cor28-2 =25.3h, SD=1.78) were significantly longer than their respective controls (23.9h, SD=1.62 and 24.0h SD=2.02) (Welch Two Sample t-test p< 0.05) as shown in Table 2. This confirms results previously reported using leaf movement, qPCR and ProCCR2:LUC bioluminescence rhythms(49,50). Cor27 mutants showed no significant difference in period length, however the double knock-out cor27-1/28-2 had an exaggerated long period phenotype (26.4h, SD=2.37).…”

“…The most significant associations had three SNPs with a –log10( p ) score of 10.4-11.5, found on chromosome 4 associated with period variation. Within this interval we identified a non-synonymous SNP in the gene COLD-REGULATED GENE 28 , a gene that has previously been identified as a negative regulator of several core clock genes ( PRR7, TOC1, PRR5 and ELF4 ) and is also implicated in the trade-off between flowering-time and freezing tolerance(49,50). The substitution resulted in a tryptophan (W) to serine (S) amino acid change at position 58 within the second exon of COR28 (Figure 4A).…”

“…We show that circadian diversity assayed by DF is genetically heritable and is associated with several highly significant polymorphisms, two of which ( ELF3 and COR28 ) had previously acknowledged circadian functions. COR28 is partially redundant with its partner COR27 and acts both upstream and downstream of the circadian clock(49,50). TDNA insertions in these genes have been shown to lengthen periods, extend flowering time and increase freezing tolerance(49,50).…”

Crosstalk of PIF4 and DELLA modulates CBF transcript and hormone homeostasis in cold response in tomato

“…It has been reported that light is essential for the development of cold acclimation in plants (Kim et al, 2002). Furthermore, the circadian clock, photoperiod and light quality also regulate plant cold tolerance (Dong et al, 2011;Franklin and Whitelam, 2007;Lee and Thomashow, 2012;Li et al, 2016b;Wang et al, 2016Wang et al, , 2018Wang et al, , 2019. CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1)-mediated and LATE-ELONGATED HYPOCOTYL (LHY)-mediated outputs from the circadian clock positively regulate plant cold tolerance through the CBF pathway in Arabidopsis (Dong et al, 2011).…”

“…Meanwhile, the CBF pathway is actively repressed by PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) and PIF7 during the warm longday season in Arabidopsis (Lee and Thomashow, 2012). Blue light and low temperature-induced COR27 and COR28 negatively regulate freezing tolerance in Arabidopsis (Li et al, 2016b), whereas a low red/far-red light ratio (L-R/FR) induces cold tolerance in both Arabidopsis and Solanum lycopersicum (Franklin and Whitelam, 2007;Wang et al, 2016Wang et al, , 2018. Intriguingly, recent work has demonstrated that Arabidopsis phytochrome B (phyB) acts as a thermosensor (Jung et al, 2016;Legris et al, 2016), and it negatively regulates cold tolerance in both Arabidopsis and tomato (Franklin and Whitelam, 2007;Wang et al, 2016Wang et al, , 2018.…”