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Peach encodes 14 INDETERMINATE DOMAIN (IDD) transcription factors. PpIDD4, -12 and -13 mediated PpDELLA1 binding to the PpGA20ox1 promoter. Each of these three PpIDD-DELLA1 complexes activated transcription of PpGA20ox1. PpTPR1 and -4 interrupted the interaction of PpIDDs with PpDELLA1. The plant growth regulator gibberellin (GA) plays an important role in the rapid growth of annual shoots in peach. Our previous study showed that the peach cultivar 'FenHuaShouXingTao' (FHSXT), a gibberellic acid receptor (gid1) mutant, accumulates active GAs in annual shoot tips. This mutant enhances GA feedback regulation in peach. The results of this study suggested that the PpIDD-DELLA1 complex is the underlying mechanism of GA feedback regulation in peach. Fourteen IDD genes were identified in peach, and three PpIDDs (PpIDD4, -12 and -13, all from group IV) interacted with PpDELLA1, an important component in GA signaling pathway. Truncation, segmentation and site mutation of the promoter of PpGA20ox1 (a GA biosynthesis gene) showed that all three PpIDD proteins recognized the core motif TTGTC. PpIDD4 and -13 mainly bind to site 3, while PpIDD12 binds to site 5 of the PpGA20ox1 promoter. All three PpIDD-DELLA1 complexes activated the PpGA20ox1 promoter-LUC fusion. These data suggested that PpIDDs bridge PpDELLA1 and the promoter of PpGA20ox1, which then activated the transcription of PpGA20ox1. In addition, PpTPR1 and -4 disrupted the interaction of PpIDDs with PpDELLA1. Our research will be helpful for understanding and possibly modifying the regulation of annual shoot growth and GA biosynthesis.

Chinese jujube (Ziziphus jujuba) is an important fruit tree in China. Jujube witches' broom (JWB) disease, caused by JWB phytoplasma (‘Candidatus phytoplasma ziziphi’), is the most devastating infectious disease of the jujube tree. Lipoxygenase (LOX) plays important roles in the jasmonic acid (JA) biosynthesis pathway and plant defense to biotic stresses. In this study, we identified 13 LOX genes in the jujube genome distributed on 5 chromosomes. The ZjLOX proteins were classified into two categories based on phylogenetic analysis. We tracked gene duplication events and found two sets of tandem repeats on chromosome 2. We predicted the promoters of the ZjLOXs using PlantCARE and found a large number of cis elements that may respond to phytohormones, light, and biological stresses. Transcriptomic, proteomic, and qRT-PCR expression analyses showed that ZjLOX02, ZjLOX05, ZjLOX06 and ZjLOX08 may play important roles in the interaction between jujube and phytoplasma. This study provides a foundation for better understanding both the molecular evolution of the jujube LOX gene family and the response of the ZjLOX genes to JWB phytoplasma infection.

Recently, there is an increased interest in the function of polyamine (PA) catabolism during fruit ripening, but little is known about its role during the ripening of peach (Prunus persica L.). In this study, the contents of both free and conjugated PAs markedly decreased as the peach fruit ripened. However, RNA-seq analysis showed that the transcript levels of PA synthesis–related genes increased, suggesting that the decreasing PA content during peach ripening was associated with PA catabolism. To better understanding the function of PA catabolism in peach ripening, genes encoding potential polyamine oxidases (PAOs), which are involved in PA catabolism, were identified across the peach genome. Four putative PAO genes (PpePAO1-PpePAO4) were identified in peach using the recently released genome database. The mRNA level of PpePAO1 was significantly increased during peach fruit ripening. Detection of free PAs in tobacco leaves transiently over-expressing PpePAO1 suggested that this gene is probably involved in terminal catabolism of PA. Treatment with the PAO inhibitor guazatine significantly reduced ethylene production and flesh softening of peach fruit, decreased the expression levels of fruit ripening-related genes, and significantly decreased the expression level of PpePAO1 and PAO activity, while PA contents were dramatically higher compared to control treatments. Our results suggests that PpePAO1-mediated PA catabolism is associated with decreased PA content during peach fruit ripening. These data provide valuable knowledge for better understanding the roles of PA catabolism in peach development and ripening.

Plant growth caused by ambient temperature is thought to be regulated by a complex transcriptional network. A temperature-sensitive peach (Prunus persica) was used to explore the mechanisms behind shoot internode elongation at elevated temperatures. There was a significantly positive correlation between the length of the terminal internode (TIL) and the maximum temperature three days prior to the measuring day. Four critical growth stages (initial period and initial elongation period at lower temperature, rapid growth period and stable growth period at higher temperature) were selected for comparative RNA-seq analysis. About 6.64G clean bases were obtained for each library, and 88.27% of the data were mapped to the reference genome. Differentially expressed gene (DEG) analysis among the three pairwise comparisons resulted in the detection of several genes related to the shoot elongation in temperature-sensitive peach. HSFAs were up-regulated in response to the elevated temperature, while the up-regulated expression of HSPs might influence hormone signaling pathways. Most of DEGs involved in auxin, abscisic acid and jasmonic acid were up-regulated, while some involved in cytokinin and brassinosteroid were down-regulated. Genes related to ethylene, salicylic acid and circadian rhythm were also differentially expressed. Genes related to aquaporins, expansins, pectinesterases and endoglucanase were up-regulated, which would promote cell elongation. These results lay a foundation for further dissection of the regulatory mechanisms underlying shoot elongation at elevated temperatures.

Phytoplasmas are plant pathogenic bacteria that inhabit the phloem sieve elements in infected plants and lack a cell wall. Infection of the woody perennial Ziziphus jujuba with phytoplasma causes jujube witches’ broom (JWB), a disease that causes heavy crop losses. The TEOSINTE BRANCHED 1/CYCLOIDEA/PCF (TCP) transcription factors (TFs) are plant-specific regulators of plant morphogenesis, development, and defense after phytoplasma infection. While the TCP gene family has been studied in many plants, there is no report on TCPs in jujube. In this study, 21 ZjTCP TFs were identified and bioinformatically analyzed based on the genome of the Dongzao cultivar. Another 2 ZjTCPs were found in the genome of the Junzao cultivar. Physicochemical properties of the ZjTCP proteins were quite varied, indicating possible versatility of functions. ZjTCP proteins ranged from 172 to 590 amino acids (aa), had isoelectric points (pIs) between 5.53 (ZjTCP1) and 9.81 (ZjTCP11), and molecular weights ranging from 19,279.98 (ZjTCP11) to 61,784.17 kDa (ZjTCP19). Interaction network mapping predicted several hubs, such as ZjTCP6, ZjTCP7, ZjTCP8, ZjTCP15, ZjTCP16, and ZjTCP19, among which ZjTCP6 and ZjTCP16 were predicted to function in plant defense and morphogenesis. Spatiotemporal expression analysis of the ZjTCPs showed that ten of the ZjTCP genes were detected after infection with ‘Candidatus Phytoplasma ziziphi’. ZjTCP6, ZjTCP7, ZjTCP16, and ZjTCP19 were up-regulated after phytoplasma infection. ZjTCP16 showed the most significant increase in transcript levels, after the emergence of disease symptoms. ZjTCP12, ZjTCP15, and ZjTCP18 were down-regulated after phytoplasma infection. We concluded that ZjTCP6 and ZjTCP16 were most likely regulatory factors with roles during the plant response to jujube witches’ broom.

Effects of salicylic acid (SA), ultraviolet radiation (UV-B and UV-C) on the trans-resveratrol (Res) inducement of the skin of harvested grape berries were studied with three grape cultivars Takasuma, Tano Red and Carigane. Split plot design tests were adopted to compare the effects of UV-B and UV-C radiation on Res inducement of different cultivars. Results showed that spraying 100 mg·L−1 SA markedly enhanced Res contents in the skins of harvested berries for the three selected cultivars. However, the effect of SA varied with the cultivars, and Res inducement by SA was more effective to Tano Red than Takasuma and Carigane. UV-B or UV-C irradiation significantly increased Res contents in grape skins and UV-C was more effective than UV-B. The effects of UV types and dosages on Res inducement depended upon cultivars. In the range of 0–3.6 kJ·m−2, the Res contents in the skins of the three grape cultivars were enhanced along with the increase of dosages of UV-B and UV-C.