Ethylene plays an important role in grape ripening, acting through ethylene response factors (ERFs) that are downstream of ethylene signaling pathways, yet little else is known about these molecular mechanisms. In our study, we demonstrate that ethylene treatment promotes grape ripening and that the transcription factor VvERF75 shows increased expression during grape ripening. VvERF75 was found to contain a conserved AP2/ERF domain, to be a member of the ERF IXa subfamily, an to localize to the nucleus and to have transactivation activity in yeast. Our in vitro assays showed that VvERF75 can positively regulate expression of pheophorbide a oxygenase (VvPAO1) and 1-aminocyclopropane-1-carboxylic acid synthase (VvACS5) by binding to DRE motifs in their promoters. Overexpression of VvERF75 in tomato increased ethylene production and resulted in dwarfed plants, early flowering and fruit ripening, increased SlPAO and SlACS transcript levels, and decreased chlorophyll content. In general, our study revealed that VvERF75 may regulate fruit ripening by promoting ethylene biosynthesis and chlorophyll degradation, a discovery that lays a foundation for deciphering the molecular mechanisms of grape ripening.

The heat shock protein 20 (HSP20) proteins comprise an ancient, diverse, and crucial family of proteins that exists in all organisms. As a family, the HSP20s play an obvious role in thermotolerance, but little is known about their molecular functions in addition to heat acclimation. In this study, 42 PpHSP20 genes were detected in the peach genome and were randomly distributed onto the eight chromosomes. The primary modes of gene duplication of the PpHSP20s were dispersed gene duplication (DSD) and tandem duplication (TD). PpHSP20s in the same class shared similar motifs. Based on phylogenetic analysis of HSP20s in peach, Arabidopsis thaliana, Glycine max, and Oryza sativa, the PpHSP20s were classified into 11 subclasses, except for two unclassified PpHSP20s. cis-elements related to stress and hormone responses were detected in the promoter regions of most PpHSP20s. Gene expression analysis of 42 PpHSP20 genes revealed that the expression pattern of PpHSP20-32 was highly consistent with shoot length changes in the cultivar ‘Zhongyoutao 14’, which is a temperature-sensitive semi-dwarf. PpHSP20-32 was selected for further functional analysis. The plant heights of three transgenic Arabidopsis lines overexpressing PpHSP20-32 were significantly higher than WT, although there was no significant difference in the number of nodes. In addition, the seeds of three over-expressing lines of PpHSP20-32 treated with high temperature showed enhanced thermotolerance. These results provide a foundation for the functional characterization of PpHSP20 genes and their potential use in the growth and development of peach.

Plant-pathogenic phytoplasmas secrete specific virulence proteins into a host plant to modulate plant function for their own benefit. Identification of phytoplasmal effectors is a key step toward clarifying the pathogenic mechanisms of phytoplasma. In this study, Zaofeng3, also known as secreted jujube witches’ broom phytoplasma protein 3 (SJP3), was a homologous effector of SAP54 and induced a variety of abnormal phenotypes, such as phyllody, malformed floral organs, witches’ broom, and dwarfism in Arabidopsis thaliana. Zaofeng3 can also induce small leaves, dwarfism, and witches’ broom in Ziziphus jujuba. Further experiments showed that the three complete α-helix domains predicted in Zaofeng3 were essential for induction of disease symptoms in jujube. Yeast two-hybrid library screening showed that Zaofeng3 mainly interacts with proteins involved in flower morphogenesis and shoot proliferation. Bimolecular fluorescence complementation assays confirmed that Zaofeng3 interacted with these proteins in the whole cell. Overexpression of zaofeng3 in jujube shoot significantly altered the expression patterns of ZjMADS19, ZjMADS47, ZjMADS48, ZjMADS77, and ZjTCP7, suggesting that overexpressing zaofeng3 might induce floral organ malformation and witches’ broom by altering the expression of the transcriptional factors involved in jujube morphogenesis.

The plant growth regulator ethylene influences rachis browning in grape (Vitis vinifera L.). Although the ethylene signaling pathway is well defined, there is limited knowledge on its mode of action during rachis browning. Here, we show that an ethylene response factor (VvERF111) positively regulates chlorophyll degradation in rachis by binding to a DRE motif in the promoter of VvCLH1. The expression of VvERF111 and VvCLH1 in rachis was induced by ethylene and inhibited by 1-methylcyclopropene (1-MCP). VvERF111 belongs to the ERF IX subfamily of the APETALA2/ethylene responsive factor (AP2/ERF) superfamily, shows transcriptional activity in yeast, and is localized in the nucleus and membrane. The transient overexpression of VvERF111 or chlorophyllase (VvCLH1) in grape leaves accelerated chlorophyll degradation. In VvERF111-overexpressing leaves, transcript levels of VvCLH1 were also increased. Our findings offer a deeper understanding of the transcriptional regulation of chlorophyll degradation during the rachis browning of grape.