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Abstract [Objective] This study aims to identify and analyze the members of the tonoplast intrinsic protein (TIP) subfamily in apple, and to investigate the expression patterns under drought stress. It provides information for further research on utilization of drought resistance gene resources in apple. [Methods] The MdTIPs in apple genome was identified by bioinformatics methods. The physicochemical properties, gene structures, conserved motifs, cis-regulatory elements, and phylogenetic trees, etc. of the subfamily members were analyzed. The expression patterns of MdTIPs in different organs under drought stress were analyzed by qRT-PCR. [Results] A total of 13 MdTIP genes were identified in the apple genome, and most members were localized at the plasma membrane. Chromosome localization analysis suggested that all members were distributed on 10 chromosomes, with 1-3 members on each chromosome. Besides, the promoter regions of the genes contained response elements for hormonal and adversity stresses. qRTPCR showed that MdTIP members were up-regulated in roots except MdTIP1;1, of which MdTIP1;3 and MdTIP1;4 were up-regulated 5.27 times and 5.69 times, respectively, compared with the control, suggesting that these two genes might be critical in response to drought stress. [Conclusion] Identification of MdTIP subfamily members is provided in this study. 10 MdTIP members are differentially expressed in roots, stems, and leaves, and 12 members are highly expressed in roots.

The PIN‐FORMED (PIN) proteins mediate the auxin flow throughout the plant and have been identified in many species. However, evolution differences in the PIN gene families have not been systematically analyzed, and their functions under abiotic stresses in grape are largely unexplored. In this study, 373 PIN genes were identified from 25 species and divided into 3 subgroups. Physicochemical properties analysis indicated that most of the PIN proteins were unstable alkaline hydrophobic proteins in nature. The synteny analysis showed that the PINs contained strong gene duplication. Motif composition revealed that PIN gene sequence differences between monocotyledons and dicotyledons were due to evolutionary‐induced base loss, and the loss was more common in dicotyledonous. Meanwhile, the codon usage bias showed that the PINs showed stronger codon preference in monocotyledons, monocotyledons biased towards C3s and G3s, and dicotyledons biased towards A3s and T3s. In addition, the VvPIN1 can interact with VvCSN5. Significantly, under freezing treatment, the ion leakage, O2·−$$ \left({O}_2^{\cdotp -}\right) $$, H2O2, and malondialdehyde (MDA) were obviously increased, while the proline (Pro) content, peroxidase (POD) activity, and glutathione (GSH) content were decreased in VvPIN1‐overexpressing Arabidopsis compared to the wild type (WT). And quantitative real‐time PCR (qRT‐PCR) showed that AtICE1, AtICE2, AtCBF1, AtCBF2, and AtCBF3 were down‐regulated in overexpression lines. These results demonstrated that VvPIN1 negatively regulated the freezing tolerance in transgenic Arabidopsis. Collectively, this study provides a novel insight into the evolution and a basis for further studies on the biological functions of PIN genes in monocotyledons and dicotyledons. [ABSTRACT FROM AUTHOR]

Cold stress adversely impacts grape growth, development, and yield. Therefore, improving the cold tolerance of grape is an urgent task of grape breeding. The Jasmonic acid (JA) pathway responsive gene JAZ plays a key role in plant response to cold stress. However, the role of JAZ in response to low temperatures in grape is unclear. In this study, VvJAZ13 was cloned from the 'Pinot Noir' (Vitis vinefera cv. 'Pinot Noir') grape, and the potential interacting protein of VvJAZ13 was screened by yeast two-hybrid (Y2H). The function of VvJAZ13 under low temperature stress was verified by genetic transformation. Subcellular localization showed that the gene was mainly expressed in cytoplasm and the nucleus. Y2H indicated that VvF-box, VvTIFY5A, VvTIFY9, Vvbch1, and VvAGD13 may be potential interacting proteins of VvJAZ13. The results of transient transformation of grape leaves showed that VvJAZ13 improved photosynthetic capacity and reduced cell damage by increasing maximum photosynthetic efficiency of photosystem II (Fv/Fm), reducing relative electrolyte leakage (REL) and malondialdehyde (MDA), and increasing proline content in overexpressed lines (OEs), which played an active role in cold resistance. Through the overexpression of VvJAZ13 in Arabidopsis thaliana and grape calli, the results showed that compared with wild type (WT), transgenic lines had higher antioxidant enzyme activity and proline content, lower REL, MDA, and hydrogen peroxide (H2O2) content, and an improved ability of scavenging reactive oxygen species. In addition, the expression levels of CBF1-2 and ICE1 genes related to cold response were up-regulated in transgenic lines. To sum up, VvJAZ13 is actively involved in the cold tolerance of Arabidopsis and grape, and has the potential to be a candidate gene for improving plant cold tolerance. [ABSTRACT FROM AUTHOR]

In this study, we obtained and cloned VvSnRK2.7 by screening transcriptomic data to investigate the function of the grape sucrose non-fermenting kinase 2 (SnRK2) gene under stress conditions. A yeast two-hybrid (Y2H) assay was used to further screen for interaction proteins of VvSnRK2.7. Ultimately, VvSnRK2.7 was heterologously expressed in Arabidopsis thaliana, and the relative conductivity, MDA content, antioxidant enzyme activity, and sugar content of the transgenic plants were determined under drought treatment. In addition, the expression levels of VvSnRK2.7 in Arabidopsis were analyzed. The results showed that the VvSnRK2.7-EGFP fusion protein was mainly located in the cell membrane and nucleus of tobacco leaves. In addition, the VvSnRK2.7 protein had an interactive relationship with the VvbZIP protein during the Y2H assay. The expression levels of VvSnRK2.7 and the antioxidant enzyme activities and sugar contents of the transgenic lines were higher than those of the wild type under drought treatment. Moreover, the relative conductivity and MDA content were lower than those of the wild type. The results indicate that VvSnRK2.7 may activate the enzyme activity of the antioxidant enzyme system, maintain normal cellular physiological metabolism, stabilize the berry sugar metabolism pathway under drought stress, and promote sugar accumulation to improve plant resistance. [ABSTRACT FROM AUTHOR]

Acidity is a determinant of the organoleptic quality of apple, whereas its regulatory mechanism under water stress remains obscure. Fruit from apple 'Yanfu 3' of Fuji trees grown under normal water irrigation (CK), excessive water deficit treatment (DRT) and excessive water irrigation treatment (WAT) were sampled at 85, 100, 115, 130, 145, 160 and 175 days after full bloom designated stages S1, S2, S3, S4, S5, S6 and S7, respectively. DRT treatment reduced the individual fruit weight and fruit moisture content, and increased fruit firmness. The malate content of DRT treatment was higher than that of CK and WAT from stages S1 to S7. RNA sequencing (RNA-seq) analysis of the transcriptome at stages S4, S6 and S7 indicated that malate anabolism was associated with cysteine and methionine, auxin signaling, glyoxylate and dicarboxylate and pyruvate metabolism. Overexpression of MdPEPC4 increased the malate content in apple calli induced by 4% PEG. Our study provides novel insights into the effects of water stress on the molecular mechanism underlying apple fruit acidity. [ABSTRACT FROM AUTHOR]

The steroidogenic acute regulatory protein‐related lipid transfer domain (STARD) forms a protein that can bind membrane‐derived phospholipid second messengers and plasma membranes. Although it has been reported in many plants, the evolutionary relationship of the STARD gene family has not been systematically analyzed, and functions of the HD‐START and HD‐START‐MEKHLA domain subgroup genes under hormone and abiotic stress are also unclear in grapes. This study identified and analyzed 23 VvSTARD genes, which were distinctly divided into five subgroups according to five conserved domain types. The analyses of codon preference, selective pressure, and synteny relationship revealed that grape had higher homology with Arabidopsis compared with rice. Interestingly, the expression levels of VvSTARD genes in subgroups 1, 2, and 3 exhibited significant upregulation under NaCl treatment at 24 h, but VvSTARD genes in subgroups 4 and 5 were upregulated under methyl jasmonate (MeJA) treatment at 24 h. The subcellular localization showed that VvSTARD5 was localized in the nucleus. Additionally, under NaCl treatment at 24 h, there were an obvious decrease in the relative electrical leakages and the content of malondialdehyde (MDA), while the relative expression level of VvSTARD5 and content of proline were obviously enhanced in three transgenic lines. Therefore, the overexpression of VvSTARD5 greatly increased the salt tolerance of transgenic tomatoes. Collectively, this study preliminarily explores the comprehensive function of the STARD gene family in grapes and verifies the function of VvSTARD5 in response to salt. [ABSTRACT FROM AUTHOR]