Phylogenetic, Molecular, and Functional Characterization of PpyCBF Proteins in Asian Pears (Pyrus pyrifolia)

Abstract

C-repeat binding factor/dehydration-responsive element (CBF/DRE) transcription factors (TFs) participate in a variety of adaptive mechanisms, and are involved in molecular signaling and abiotic stress tolerance in plants. In pear (Pyrus pyrifolia) and other rosaceous crops, the independent evolution of CBF subfamily members requires investigation to understand the possible divergent functions of these proteins. In this study, phylogenetic analysis divided six PpyCBFs from the Asian pear genome into three clades/subtypes, and collinearity and phylogenetic analyses suggested that PpyCBF3 was the mother CBF. All PpyCBFs were found to be highly expressed in response to low temperature, salt, drought, and abscisic acid (ABA) as well as bud endodormancy, similar to PpyCORs (PpyCOR47, PpyCOR15A, PpyRD29A, and PpyKIN). Transcript levels of clade II PpyCBFs during low temperature and ABA treatments were higher than those of clades I and III. Ectopic expression of PpyCBF2 and PpyCBF3 in Arabidopsis enhanced its tolerance against abiotic stresses, especially to low temperature in the first case and salt and drought stresses in the latter, and resulted in lower reactive oxygen species (ROS) and antioxidant gene activities compared with the wild type. The increased expression of endogenous ABA-dependent and -independent genes during normal conditions in PpyCBF2- and PpyCBF3-overexpressing Arabidopsis lines suggested that PpyCBFs were involved in both ABA-dependent and -independent pathways. All PpyCBFs, especially the mother CBF, had high transactivation activities with 6XCCGAC binding elements. Luciferase and Y1H assays revealed the existence of phylogenetically and promoter-dependent conserved CBF–COR cascades in the pear. The presence of a previously identified CCGA binding site, combined with the results of mutagenesis of the CGACA binding site of the PpyCOR15A promoter, indicated that CGA was a core binding element of PpyCBFs. In conclusion, PpyCBF TFs might operate redundantly via both ABA-dependent and -independent pathways, and are strongly linked to abiotic stress signaling and responses in the Asian pear.

ABA‐responsive ABRE‐BINDING FACTOR3 activatesDAM3expression to promote bud dormancy in Asian pear

“…In a previous study, we observed that PpyCBF4 expression is induced by ABA and activates the PpyDAM3 promoter (Ahmad et al, ; Li et al, ). Because we also identified ABREs in the PpyCBF4 promoter region (Figure S6b), we examined whether PpyABF3 is expressed downstream of the ABA pathway and upstream of PpyCBF4 expression.…”

Characterization of PcLEA14, a Group 5 Late Embryogenesis Abundant Protein Gene from Pear (Pyrus communis)

“…The distinct difference in the expression patterns found in the DREB1 subfamily could be associated with their physiological roles. A recent study in P. pyrifolia conducted expression analysis of the DREB family gene [ 36 ]. Although data was not collected year-round, the expression levels of all genes peaked between October and February and no members with unique expression such as DREB1B , DREB1D , and DREB1E were reported.…”

Chromosomal Distribution of Genes Conferring Tolerance to Abiotic Stresses Versus That of Genes Controlling Resistance to Biotic Stresses in Plants

“…The abiotic stresses studied include cold, heat, drought, salt, iron deficiency, nitrogen deficiency, UV irradiation, DNA damage, reducing agent, phytohormones (GA, SA, JA, ABA, ethylene, 2,4-D, and NAA), and heavy metals (cadmium, nickel and cobalt). Two [6,7] of the 21 articles did not present information on the chromosomal locations of genes for abiotic-stress tolerance, and one [18] did not map the BocMBF1c gene to the target species B. oleracea but did locate the orthologous gene identified in A. thaliana to the proximal section of chromosome 3.…”

“…Many transcription factor gene families (TFs) were studied in the majority of these 21 articles [6,8,9,11,[13][14][15][16][17][18][19][20]23,24]. Various putative stress-related and hormone-responsive cis-acting regulatory elements were identified in the promotor of these TFs.…”