CaMYB340 homo- and heterodimers mediate chilling injury in bell pepper
by participating in fatty acid desaturation and the ICE-CBF pathway
Bell pepper ( Capsicum annuum L.) is a tradable and desirable
crop; however, its perishable nature requires low-temperature handling.
postharvest waste. Current knowledge about CI in pepper is limited. The
mechanism of CI is multi-faceted; thus, this study focused on fatty acid
desaturation and identified an upstream nuclear transcription factor
(TF) CaMYB340 belonging to the R2R3 MYB subfamily that negatively
regulates fatty acid desaturation and the ICE-CBF pathway, and is
induced by low temperature (4°C) at the DNA and transcriptional levels.
Specifically, McrBC treatment and bisulfite sequencing PCR indicate that
exposure to cold triggers DNA methylation on one of the CHH sites in the
CaMYB340 promoter. This epigenetic event at least partly
contributes to the upregulation of CaMYB340 transcripts.
Increased expression of CaMYB340 results in the formation of protein
complexes with CaMYB340, CabHLH93, and CaMYB1R1 that in turn
downregulates the expression of downstream genes. For peppers held at
low temperature, transient overexpression of CaMYB340 reduced
unsaturated fatty acid (FA) content and membrane fluidity, resulting in
cold-induced poor peel texture. Overall, these results underscore the
intricacy of transcriptional networks in plants and highlight the role
of CaMYB340 in CI occurrence in pepper fruits.