ERF9 of Poncirus trifoliata (L.) Raf. undergoes feedback regulation by ethylene and modulates cold tolerance via regulating a glutathione S‐transferase U17 gene

Abstract

Summary Plant ethylene‐responsive factors (ERFs) play essential roles in cold stress response, but the molecular mechanisms underlying this process remain poorly understood. In this study, we characterized PtrERF9 from trifoliate orange (Poncirus trifoliata (L.) Raf.), a cold‐hardy plant. PtrERF9 was up‐regulated by cold in an ethylene‐dependent manner. Overexpression of PtrERF9 conferred prominently enhanced freezing tolerance, which was drastically impaired when PtrERF9 was knocked down by virus‐induced gene silencing. Global transcriptome profiling indicated that silencing of PtrERF9 resulted in substantial transcriptional reprogramming of stress‐responsive genes involved in different biological processes. PtrERF9 was further verified to directly and specifically bind with the promoters of glutathione S‐transferase U17 (PtrGSTU17) and ACC synthase1 (PtrACS1). Consistently, PtrERF9‐overexpressing plants had higher levels of PtrGSTU17 transcript and GST activity, but accumulated less ROS, whereas the silenced plants showed the opposite changes. Meanwhile, knockdown of PtrERF9 decreased PtrACS1 expression, ACS activity and ACC content. However, overexpression of PtrERF9 in lemon, a cold‐sensitive species, caused negligible alterations of ethylene biosynthesis, which was attributed to perturbed interaction between PtrERF9, along with lemon homologue ClERF9, and the promoter of lemon ACS1 gene (ClACS1) due to mutation of the cis‐acting element. Taken together, these results indicate that PtrERF9 acts downstream of ethylene signalling and functions positively in cold tolerance via modulation of ROS homeostasis by regulating PtrGSTU17. In addition, PtrERF9 regulates ethylene biosynthesis by activating PtrACS1 gene, forming a feedback regulation loop to reinforce the transcriptional regulation of its target genes, which may contribute to the elite cold tolerance of Poncirus trifoliata.

The miR164a‐NAM3 module confers cold tolerance by inducing ethylene production in tomato

“…In Poncirus trifoliata L. Raf., ethylene‐induced ERF transcription factor PtrERF9, plays a positive role in cold tolerance (Zhang et al., 2022). By contrast, ethylene negatively regulates cold tolerance in Medicago truncatula (Zhao et al., 2014) and A. thaliana (Shi et al., 2012).…”

Discovery of cold-resistance genes in Vitis amurensis using bud-based quantitative trait locus mapping and RNA-seq

“…Multiple GST genes in pumpkin are induced by cold environments [ 40 ]. PtrERF9 improves cold resistance by promoting the expression of PtrGSTU17 and reducing ROS content in trifoliate orange under cold stress [ 41 ]. Until now, GST genes involved in grape cold resistance have not been reported.…”

“…Expression of IAA27 and SAUR71 was significantly upregulated in ‘SY’ under cold stress, indicating that they could be used as candidate genes for further research into the mechanism of auxin in regulating grape cold resistance. In recent years, an increasing number of studies have reported the important regulation effect of ERF in the cold resistance of fruit trees [ 41 , 48 , 52 , 53 ]. ERF genes involved in grape cold resistance have also been reported, including VaERF057 [ 54 ] and VaERF092 [ 5 ].…”

“…Interestingly, previous studies have shown potential interactions of these candidate genes in cold resistance. For example, the interaction between MdMYB308L and MdbHLH33 could positively regulate the cold resistance in apple [ 57 ] and PtrERF9 acts downstream of ethylene signaling and functions positively in cold tolerance via regulating PtrGSTU17 in Citrus [ 41 ].…”

Genome-Wide Identification, Characterization, and Expression Analysis Related to Low-Temperature Stress of the CmGLP Gene Family in Cucumis melo L.

“…The promoter fragment of CmGLP2-5 was recombined to the pGreen 0800-LUC vector to generate the reporter. The constructs were co-transformed into tobacco seedlings as described in a previous report [ 69 ]. The transformed tobacco seedlings were cultured in the dark for 2 days to conduct a dual luciferase assay.…”