MdTCP46 interacts with MdABI5 to negatively regulate ABA signalling and drought response in apple

Abstract

TEOSINTE BRANCHED 1/CYCLOIDEA/PCF (TCP) transcription factors play crucial roles in plant abiotic stresses. However, little is known about the role of TCP genes in the drought stress tolerance of apple. Here, we found that abscisic acid (ABA) and drought treatment reduced the expression of MdTCP46, and overexpression of MdTCP46 reduced ABA sensitivity and drought stress resistance. MdTCP46 was found to interact with MdABI5 both in vitro and in vivo, and this interaction was essential for drought resistance via the ABA-dependent pathway. Overexpression of MdABI5 enhanced ABA sensitivity and drought stress resistance by directly activating the expression of MdEM6 and MdRD29A. MdTCP46 significantly suppressed the transcriptional activity of MdABI5, thereby negatively regulating MdABI5-mediated ABA signalling and drought response. Overall, our results demonstrate that the MdTCP46-MdABI5-MdEM6/MdRD29A regulatory module plays a key role in the modulation of ABA signalling and the drought stress response. These findings provide new insight into the role of MdTCP46 in ABA signalling and abiotic stress responses.

Physiological Roles and Mechanisms of Action of Class I TCP Transcription Factors

“…Notably, although these findings reveal TCPs as positive regulators of ABA-mediated abiotic stress tolerance, a negative effect on ABA biosynthesis and signaling was reported for a group of class I TCP members. In apple, MdTCP46 reduces the expression of MdABI5 and its transcriptional activity by interfering with its binding to MdEM6 and MdRD29A target genes, and thus reducing the ABA-dependent drought response [ 24 ] ( Table S1 ). GhTCP19 inhibits ABA biosynthesis directly repressing GhNCED to promote corm dormancy release in gladiolus [ 125 ] and TCP14 inhibits the expression of the ABA biosynthesis gene ABA1 to promote seed germination in Arabidopsis [ 71 , 72 ].…”

“…Since ABA is an inhibitor of processes promoted by TCPs (e.g., plant growth and reproduction and cell division and elongation) a mutual repression between class I TCP activity and ABA signaling pathways is expected. According to this, the expression of MdTCP46 is repressed by ABA and drought conditions in apple [ 24 ]. However, despite increasing reports in this area, the molecular network connecting TCP function with ABA-dependent signaling pathways are far from being understood.…”

“…Although most of the class I TCP proteins have been reported as transcriptional activators, a number of reports indicate that they can also act as repressors. TCP16 and TCP21/CHE1 from Arabidopsis , PpTCP20 from peach, and GhTCP19 from cotton repress the expression of their target genes [ 26 , 125 , 135 , 136 ], MdTCP46 from apple blocks the binding of a transcriptional activator to its target genes, thereby negatively regulating their expression [ 24 ], and some TCPs interact with transcriptional repressors [ 137 ]. Even more, different class I TCPs can act as activators or repressors of the same target gene, as CCA1 , which is activated by TCP20 and TCP22 and repressed by TCP21/CHE in Arabidopsis [ 99 , 136 ].…”

“…However, they are not present in the unicellular algae Chlamydomonas [ 6 ]. Besides Arabidopsis , TCPs were characterized in several land plants, as rice, tomato, soybean, cotton, chrysanthemum, peach, apple, Setaria italica and Setaria viridis [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ], among others. In addition, genome-wide analysis allowed the identification of TCP genes in numerous species of commercial interest, as tobacco, banana, Brassica napus , cucumber, watermelon, strawberry, eggplant, Ginkgo biloba , and tea [ 22 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ].…”

MdHB7‐like positively modulates apple salt tolerance by promoting autophagic activity and Na+ efflux

“…Ten-ll aliquots of each 10-fold serial dilution (1, 10 1 , 10 2 , and 10 3 ) were spotted onto SDbase (-Trp/-Leu) and SD-base (-Trp/-Leu/-His) media supplemented with or without 3-AT. Details on the methods are provided in previous studies (Liu et al, 2022(Liu et al, , 2023Yang et al, 2023).…”