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The MYB (v-MYB avian myeloblastosis viral oncogene homolog) transcription factor (TF) family has numerous members with complex and diverse functions, which play an indispensable role in regulating the response of plants to stress. In this study, a new 1R-MYB TF gene was obtained from Fragaria vesca (a diploid strawberry) by cloning technology and given a new name, FvMYB114. According to the subcellular localization results, FvMYB114 protein was a nuclear localization protein. Overexpression of FvMYB114 greatly enhanced the adaptability and tolerance of Arabidopsis thaliana to salt and low temperature. Under salt and cold stress, the transgenic plants had greater proline and chlorophyll contents and higher activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) than the wild-type (WT) and unloaded-line (UL) A. thaliana. However, malondialdehyde (MDA) was higher in the WT and UL lines. These results suggested that FvMYB114 may be involved in regulating the response of A. thaliana to salt stress and cold stress. FvMYB114 can also promote the expression of genes, such as the genes AtSOS1/3, AtNHX1 and AtLEA3 related to salt stress and the genes AtCCA1, AtCOR4 and AtCBF1/3 related to cold stress, further improving the tolerance of transgenic plants to salt and cold stress.

Abiotic stresses, such as iron deficiency and high salinity, affect apple growth and development. WRKY transcription factors (TFs) are widely involved in the responses of plants to adverse stresses. In the present study, a new WRKY gene was isolated from Malus xiaojinensis and designated as MxWRKY53. Subcellular localization showed that MxWRKY53 was localized to the nucleus. The expression level of MxWRKY53 was highly affected by salt, low Fe, and high Fe stresses in M. xiaojinensis seedlings. When MxWRKY53 was introduced into Arabidopsis thaliana, it greatly enhanced the salt and Fe tolerance. When dealt with high and low Fe stresses, the overexpression of MxWRKY53 in transgenic A. thaliana resulted in higher levels of root length, fresh weight, and contents of chlorophyll and Fe than wild type (WT). Increased expression of MxWRKY53 in transformed A. thaliana also contributed to higher contents of chlorophyll and proline, and higher activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), while malondialdehyde (MDA) content was lower, especially in response to salt stress. Therefore, these results show that MxWRKY53 plays a positive role in the process of plant resistance to salt, low Fe, and high Fe stresses.

Abscisic acid (ABA) plays an important role in the adaptive response to environmental stress. The rate-limiting step of ABA biosynthesis is the oxidative cleavage of cis-epoxide carotenoid catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). In this study, the ORF sequence of RiNCED1 in raspberry fruit was isolated to study the function of this gene under abiotic stress. While RiNCED1 was induced by cold, high salinity, heat, and ABA, it highly expressed in new leaves using quantitative real-time PCR. The overexpression of RiNCED1 in Arabidopsis improved the content of ABA in transgenic plants both in high salt and cold conditions. This indicated that overexpressing of RiNCED1 increased the content of ABA in Arabidopsis, which proved that RiNCED1 was involved in ABA biosynthesis. Furthermore, overexpressing of RiNCED1 lead to higher chlorophyll content, higher proline content; higher peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) activities; and lower malondialdehyde (MDA) content under high salt and cold stress. These results indicated that overexpression of RiNCED1 increased the resistance to high salt and low temperature in Arabidopsis. This study provided gene resources for breeding Rubus idaeus L. even other stress-tolerant fruit trees.

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The MYB transcription factor (TF) family is one of the largest transcription families in plants, which is widely involved in the responses to different abiotic stresses, such as salt, cold, and drought. In the present study, a new MYB TF gene was cloned from Fragaria vesca (a diploid strawberry) and named FvMYB82. The open reading frame (ORF) of FvMYB82 was found to be 960 bp, encoding 319 amino acids. Sequence alignment results and predictions of the protein structure indicated that the FvMYB82 contained the conserved R2R3-MYB domain. Subcellular localization analysis showed that FvMYB82 was localized onto the nucleus. Furthermore, the qPCR showed that the expression level of FvMYB82 was higher in new leaves and roots than in mature leaves and stems. When dealing with different stresses, the expression level of FvMYB82 in F. vesca seedlings changed markedly, especially for salt and cold stress. When FvMYB82 was introduced into Arabidopsis thaliana, the tolerances to salt and cold stress of FvMYB82-OE A. thaliana were greatly improved. When dealt with salt and cold treatments, compared with wild-type and unloaded line (UL) A. thaliana, the transgenic lines had higher contents of proline and chlorophyll, as well as higher activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). However, the transgenic A. thaliana had lower level of malondialdehyde (MDA) and electrolytic leakage (EL) than wild-type and UL A. thaliana under salt and cold stress. Meanwhile, FvMYB82 can also regulate the expression of downstream genes associated with salt stress (AtSnRK2.4, AtSnRK2.6, AtKUP6, and AtNCED3) and cold stress (AtCBF1, AtCBF2, AtCOR15a, and AtCOR78). Therefore, these results indicated that FvMYB82 probably plays an important role in the response to salt and cold stresses in A. thaliana by regulating downstream related genes.

CBF transcription factors (TFs) are key regulators of plant stress tolerance and play an integral role in plant tolerance to adverse growth environments. However, in the current research situation, there are few reports on the response of the CBF gene to Begonia stress. Therefore, this experiment investigated a novel CBF TF gene, named MbCBF2, which was isolated from M. baccata seedlings. According to the subcellular localization results, the MbCBF2 protein was located in the nucleus. In addition, the expression level of MbCBF2 was higher in new leaves and roots under low-temperature and high-salt induction. After the introduction of MbCBF2 into Arabidopsis thaliana, the adaptability of transgenic A. thaliana to cold and high-salt environments was significantly enhanced. In addition, the high expression of MbCBF2 can also change many physiological indicators in transgenic A. thaliana, such as increased chlorophyll and proline content, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activity, and reduced malondialdehyde (MDA) content. Therefore, it can be seen from the above results that MbCBF2 can positively regulate the response of A. thaliana to low-temperature and osmotic stress. In addition, MbCBF2 can also regulate the expression of its downstream genes in transgenic lines. It can not only positively regulate the expression of the downstream key genes AtCOR15a, AtERD10, AtRD29a/b and AtCOR6.6/47, related to cold stress at low temperatures, but can also positively regulate the expression of the downstream key genes AtNCED3, AtCAT1, AtP5CS, AtPIF1/4 and AtSnRK2.4, related to salt stress. That is, the overexpression of the MbCBF2 gene further improved the adaptability and tolerance of transgenic plants to low-temperature and high-salt environments.

The MYB transcription factor (TF) family is one of the largest transcription families in plants, which is widely involved in the responses to different abiotic stresses, such as salt, cold, and drought. In the present study, a new MYB TF gene was cloned from

In the life cycle of apple, it will suffer a variety of abiotic stresses, such as iron stress and salt stress. bHLH transcription factors (TFs) play an indispensable role in the response of plants to stress. In this study, a new bHLH gene named MxbHLH18 was separated from Malus xiaojinensis. According to the results of subcellular localization, MxbHLH18 was localized in the nucleus. Salt stress and iron stress affected the expression of MxbHLH18 in Malus xiaojinensis seedlings to a large extent. Due to the introduction of MxbHLH18, the resistance of Arabidopsis thaliana to salt, high iron and low iron was significantly enhanced. Under the environmental conditions of high iron and low iron, the overexpression of MxbHLH18 increased many physiological indexes of transgenic Arabidopsis compared to wild type (WT), such as root length, fresh weight and iron content. The high level expression of MxbHLH18 in transformed Arabidopsis thaliana can not only increased the content of chlorophyll and proline, as well as increasing the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT); it also reduced the content of malondialdehyde (MDA), which was more obvious under high salt conditions. In addition, the relative conductivity, H2O2 content and O2− content in transgenic Arabidopsis decreased under salt stress. Meanwhile, MxbHLH18 can also regulate the expression of downstream genes associated with salt stress (AtCBF1/2/3, AtKIN1 and AtCOR15a/b) and iron stress (AtIRT1, AtFRO2, AtNAS2, ATACT2, AtZIF1 and AtOPT3). Therefore, MxbHLH18 can actively promote the adaptability of plants to the growth environment of salt and low and/or iron.

Abiotic stress, such as drought, salt, and cold, affects normal plant growth. Ethylene response factors (ERFs) play an important role in the responses of plants to different stresses. An ERF gene was cloned from Malus baccata (L.) Borkh and named as MbERF12. A subcellular localization study proved that MbERF12 was a nucleus-localized protein. The expression level of MbERF12 was higher in stems and roots, which was markedly affected by high salinity, low temperature, and ethephon treatments. When MbERF12 was transformed into Arabidopsis thaliana, it obviously improved salt and low-temperature tolerance in transformed plants. Overexpression of MbERF12 in transformed A. thaliana also led to higher levels of peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD) and higher contents of ethylene, chlorophyll, and proline, while the content of malondialdehyde (MDA) was lower, especially when being dealt with low-temperature and high-salinity stresses. MbERF12 plays a key role in the response to salt and cold stresses in Arabidopsis by improving the scavenging ability for reactive oxygen species (ROS) through ethylene signal transduction. We proposed that MbERF12 may function as a positive regulator for abiotic stress responses and can be considered as a potential gene for improvement of cold and high-salinity tolerance in plants.

Malus xiaojinensis Cheng et Jiang is a special and significant germplasm resource of semi-dwarf apple in China. Abiotic stresses, such as Fe and high salinity, affect Malus xiaojinensis growth and development. WRKY transcription factors (TFs) are widely involved in the responses of plants to different stresses. In the present study, a new WRKY gene was isolated from Malus xiaojinensis and designated as MxWRKY64. Subcellular localization showed that MxWRKY64 was a nucleus localized protein. The expression level of MxWRKY64 was highly affected by Fe and salt stress in M. xiaojinensis seedlings. When MxWRKY64 was introduced into Arabidopsis thaliana, it greatly increased the Fe and salt tolerance in transgenic plant. When dealt with Fe stress, overexpression of MxWRKY64 in transgenic A. thaliana contributed to higher levels of fresh weight, root length, and contents of chlorophyll and Fe than wild type (WT). Increased expression of MxWRKY64 in transgenic A. thaliana also resulted in higher activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), higher contents of proline and chlorophyll, while malondialdehyde (MDA) content was lower, especially in response to salt stress. Therefore, these results suggest that MxWRKY64 probably plays an important role in response to Fe and salt stress in Arabidopsis.

In the life cycle of apple, it will suffer a variety of abiotic stresses, such as iron stress and salt stress. bHLH transcription factors (TFs) play an indispensable role in the response of plants to stress. In this study, a new

CBFs play a crucial role when plants are in adverse environmental conditions for growth. However, there are few reports on the role of CBF gene in stress responses of Malus plant. In this experiment, a new CBF TF was separated from M. baccata which was named MbCBF1. MbCBF1 protein was found to be localized in the nucleus after subcellular localization. Furthermore, the expression of MbCBF1 was highly accumulated in new leaves and roots due to the high influence of cold and high salt in M. baccata seedlings. After introducing MbCBF1 into A. thaliana, transgenic A. thaliana can better adapt to the living conditions of cold and high salt. The increased expression of MbCBF1 in A. thaliana also increased the contents of proline, remarkablely improved the activities of SOD, POD and CAT, but the content of MDA was decreased. Although the chlorophyll content also decreased, it decreased less in transgenic plants. In short, above date showed that MbCBF1 has a positive effect on improving A. thaliana cold and high salt tolerance. MbCBF1 can regulate the expression of its downstream gene in transgenic lines, up-regulate the expression of key genes COR15a, RD29a/bandCOR6.6/47 related to low temperature under cold conditions and NCED3, CAT1, P5CS1, RD22, DREB2A,PIF1/4, SOS1 and SnRK2.4 related to salt stress under high salt conditions, so as to further improve the adaptability and tolerance of the transgenic plants to low temperature and high salt environment.

The MYB transcription factor (TF) family is one of the largest transcription families in plants, which is widely involved in the responses of plants to biotic and abiotic stresses, as well as plant growth, development, and metabolic regulation. In the present study, a new MYB TF gene, MbMYB108, from Malus baccata (L.) Borkh, was identified and characterized. The open reading frame (ORF) of MbMYB108 was found to be 903 bp, encoding 300 amino acids. Sequence alignment results and predictions of the protein structure indicated that the MbMYB108 protein contained the conserved MYB domain. Subcellular localization showed that MbMYB108 was localized to the nucleus. The expression of MbMYB108 was enriched in young and mature leaves, and was highly affected by cold and drought treatments in M. baccata seedlings. When MbMYB108 was introduced into Arabidopsis thaliana, it greatly increased the cold and drought tolerances in the transgenic plant. Increased expression of MbMYB108 in transgenic A. thaliana also resulted in higher activities of peroxidase (POD) and catalase (CAT), higher contents of proline and chlorophyll, while malondialdehyde (MDA) content and relative conductivity were lower, especially in response to cold and drought stresses. Therefore, these results suggest that MbMYB108 probably plays an important role in the response to cold and drought stresses in A. thaliana by enhancing the scavenging capability for reactive oxygen species (ROS).

Apple, as one of the most important economic forest tree species, is widely grown in the world. Abiotic stresses, such as high salinity and iron deficiency, affect apple growth and development. WRKY transcription factors (TFs) are widely involved in the responses of plants to adverse stresses. In the present study, a new WRKY gene was isolated from Malus xiaojinensis and designated as MxWRKY55. Subcellular localization showed that MxWRKY55 was localized to the nucleus. The expression level of MxWRKY55 was highly affected by salt, low-Fe, and high-Fe stresses in M. xiaojinensis seedlings. When MxWRKY55 was introduced into Arabidopsis thaliana, it greatly enhanced the salt and Fe tolerance. When dealt with high- and low-Fe stresses, the overexpression of MxWRKY55 in transgenic A. thaliana resulted in higher levels of root length and fresh weight as well as contents of chlorophyll and Fe than wild type (WT). Increased expression of MxWRKY55 in transformed A. thaliana also contributed to higher contents of chlorophyll and proline and higher activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), while malondialdehyde (MDA) content was lower, especially in response to salt stress. Therefore, these results show that MxWRKY55 plays a positive role in the process of plant resistance to salt, low-Fe, and high-Fe stresses.

NAC (no apical meristem [NAM], Arabidopsis thaliana transcription activation factor [ATAF1/2], and cup-shaped cotyledon [CUC2]) TFs are involved in stress responses in plants. However, their roles in abiotic stresses are still not well known in Malus plants. In the present study, MbNAC29 from Malus baccata was identified and characterized. Quantitative real-time PCR analysis revealed that the expression of MbNAC29 was induced by cold, high salinity, drought, and heat. The open reading frame (ORF) of MbNAC29 is 1122 bp, encodes 373 amino acids. Subcellular localization showed that the MbNAC29-GFP (green fluorescent protein) fusion protein was localized in the nucleus. Furthermore, MbNAC29 was highly expressed in new leaf and mature leaf. When MbNAC29 was introduced into Arabidopsis, it improved cold and high salinity tolerance in transgenic plants under low-temperature stress (− 4°C) and salt stress (200 mM NaCl). When MbNAC29 was introduced into Arabidopsis, it increased the survival rate of transgenic lines than wild type (WT) under cold and high-salinity stresses. In addition, overexpression of MbNAC29 in transgenic Arabidopsis increased the contents of chlorophyll and proline and the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), while decreased the content of malondialdehyde (MDA). Therefore, these results suggest that MbNAC29 probably plays an important role in response to cold and salt stresses in Arabidopsis by enhancing scavenging capability of reactive oxygen species (ROS).

In the natural environment, plants often face unfavorable factors such as drought, cold, and freezing, which affect their growth and yield. The MYB (v-myb avian myeloblastosis viral oncogene homolog) transcription factor family is widely involved in plant responses to biotic and abiotic stresses. In this study

WRKY transcription factors are widely involved in abiotic stress responses in plants. However, their roles in the abiotic stresses of Malus plants are still not well known. In this study, a WRKY gene is isolated from Malus baccata (L.) Borkh. and designated as MbWRKY5. MbWRKY5 contains two WRKY domains and one Cys2-His2 (C2H2) zinc-finger motif, and was localized in the nucleus. The expression levels of MbWRKY5 were up-regulated by salinity, heat, cold, drought, and abscisic acid treatments in M. baccata seedlings. When MbWRKY5 was introduced into tobacco, an improvement in tolerance to drought and salt was achieved in transgenic plants. Under drought and salt treatments, transgenic plants had higher contents of chlorophyll, proline, glutathione, and ascorbate, and increased activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) than wild-type (WT) tobaccos. Compared with WT plants, overexpression of MbWRKY5 in transgenic tobacco also led to decreased levels of malondialdehyde and hydrogen peroxide (H2O2) under drought and salt stresses. Moreover, the MbWRKY5-OE tobaccos increased the expression levels of stress-related genes involved in oxidative stress response (NtPOD, NtSOD and NtCAT) and membrane protection (NtLEA5, NtERD10D, and NtP5CS), especially under drought and salt stresses. These results suggest that the MbWRKY5 gene plays a positive regulatory role in drought and salt stress responses.

With the increase in plastic pollution of farmland substrate, biodegradable mulch film research has become a hotspot. However, the degradation rate of biodegradable plastic film over the entire crop growth period is still unclear, as well as its impact on crop growth and product quality. Here, several properties of two kinds of composite biodegradable mulch films, PBAT/PLA-[S1] and PBAT/lignin-[S2], are studied with polyethylene-[PE] and uncovered substrate (CK) as controls. We tested the differences in morphological characterization, physical properties, and weight loss rate of the plastic films, as well as the effects of the different plastic films on melon yield and quality, substrate temperature and humidity, physical and chemical properties of the substrate, and substrate fungal species composition. Compared to PE, biodegradable plastic films S1 and S2 increased substrate temperature and the net photosynthetic rate of leaves. The results of substrate 18 s rDNA assay of CK, PE, S1, and S2 after 80 days of treatment and pre-treatment showed that a total of 12 fungal phylum, with 317 fungal genera were found, in which Ascomycota as the main phyla and Penicillium as the main genera. Compared with PE, the S2 treatment significantly increased the single fruit weight, central sugar content and soluble sugar of melon by 225.35 g, 1.26%, and 0.68%, respectively (p0.05). When buried for 240 d, the weight loss rate of S2 was significantly increased by 86.08% compared with PE (p0.05). From these results, we extrapolated that covering the substrate with the most biodegradable film, PBAT/lignin composite (10 μm), improved the yield and fruit quality of the melon in winter greenhouse production.

Apple, as one of the most important economic forest tree species, is widely grown in the world. Abiotic stress, such as low temperature and high salt, affect apple growth and development. Ethylene response factors (ERFs) are widely involved in the responses of plants to biotic and abiotic stresses. In this study, a new ethylene response factor gene was isolated from Malus baccata (L.) Borkh and designated as MbERF11. The MbERF11 gene encoded a protein of 160 amino acid residues with a theoretical isoelectric point of 9.27 and a predicated molecular mass of 17.97 kDa. Subcellular localization showed that MbERF11 was localized to the nucleus. The expression of MbERF11 was enriched in root and stem, and was highly affected by cold, salt, and ethylene treatments in M. baccata seedlings. When MbERF11 was introduced into Arabidopsis thaliana, it greatly increased the cold and salt tolerance in transgenic plant. Increased expression of MbERF11 in transgenic A. thaliana also resulted in higher activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), higher contents of proline and chlorophyll, while malondialdehyde (MDA) content was lower, especially in response to cold and salt stress. Therefore, these results suggest that MbERF11 probably plays an important role in the response to cold and salt stress in Arabidopsis by enhancing the scavenging capability for reactive oxygen species (ROS).

NAC (no apical meristem (NAM), Arabidopsis thaliana transcription activation factor (ATAF1/2) and cup shaped cotyledon (CUC2)) transcription factors play crucial roles in plant development and stress responses. Nevertheless, to date, only a few reports regarding stress-related NAC genes are available in Malus baccata (L.) Borkh. In this study, the transcription factor MbNAC25 in M. baccata was isolated as a member of the plant-specific NAC family that regulates stress responses. Expression of MbNAC25 was induced by abiotic stresses such as drought, cold, high salinity and heat. The ORF of MbNAC25 is 1122 bp, encodes 373 amino acids and subcellular localization showed that MbNAC25 protein was localized in the nucleus. In addition, MbNAC25 was highly expressed in new leaves and stems using real-time PCR. To analyze the function of MbNAC25 in plants, we generated transgenic Arabidopsis plants that overexpressed MbNAC25. Under low-temperature stress (4 &deg, C) and high-salt stress (200 mM NaCl), plants overexpressing MbNAC25 enhanced tolerance against cold and drought salinity conferring a higher survival rate than that of wild-type (WT). Correspondingly, the chlorophyll content, proline content, the activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) were significantly increased, while malondialdehyde (MDA) content was lower. These results indicated that the overexpression of MbNAC25 in Arabidopsis plants improved the tolerance to cold and salinity stress via enhanced scavenging capability of reactive oxygen species (ROS).

Cucumber is an important vegetable crop bearing fleshy pepo fruit harvested immature. Fruits left unpicked in time during summer production, as well as unfavorable environmental conditions during post-harvest shelf, will cause cucumber fruits to turn yellow and ripen, and thus impair the market value. Identification of maturity-related genes is of great agricultural and economic importance for cucumber production. Here, we isolated and characterized a MADS-box gene, Cucumis sativus SHATTERPROOF (CsSHP) in cucumber. Expression analysis indicated that CsSHP was specifically enriched in reproductive organs including stamens and carpels. Ectopic expression of CsSHP was unable to rescue the indehiscence silique phenotype of shp1 shp2 mutant plant in Arabidopsis. Instead, overexpression of CsSHP resulted in early flowering, precocious phenotypes, and capelloid organs in wild-type Arabidopsis. Biochemical analysis indicated that CsSHP directly interacted with cucumber SEPALLATA (SEP) proteins. CsSHP expression increased significantly during the yellowing stage of cucumber ripening, and was induced by exogenous application of abscisic acid (ABA). Therefore, CsSHP may participate in fruit maturation through the ABA pathway and floral organ specification via interaction with CsSEPs to form protein complex in cucumber.

In the natural environment, plants often face unfavorable factors such as drought, cold, and freezing, which affect their growth and yield. The MYB (v-myb avian myeloblastosis viral oncogene homolog) transcription factor family is widely involved in plant responses to biotic and abiotic stresses. In this study, Malus baccata (L.) Borkh was used as the research material, and a gene MbMYB4 of the MYB family was cloned from it. The open reading frame (ORF) of MbMYB4 was found to be 762 bp, encoding 253 amino acids; sequence alignment results and predictions of the protein structure indicated that the MbMYB4 protein contained the conserved MYB domain. Subcellular localization showed that MbMYB4 was localized in the nucleus. In addition, the use of quantitative real-time PCR (qPCR) technology found that the expression of MbMYB4 was enriched in the young leaf and root, and it was highly affected by cold and drought treatments in M. baccata seedlings. When MbMYB4 was introduced into Arabidopsis thaliana, it greatly increased the cold and drought tolerance in the transgenic plant. Under cold and drought stresses, the proline and chlorophyll content, and peroxidase (POD) and catalase (CAT) activities of transgenic A. thaliana increased significantly, and the content of malondialdehyde (MDA) and the relative conductivity decreased significantly, indicating that the plasma membrane damage of transgenic A. thaliana was lesser. Therefore, the overexpression of the MbMYB4 gene in A. thaliana can enhance the tolerance of transgenic plants to cold and drought stresses.

WRKY transcription factors are involved in stress responses in plants; however, their roles in abiotic stresses are still not well known in Malus plants. In the present study, a WRKY gene was isolated from Malus baccata (L.) Borkh and designated as MbWRKY1. Subcellular localization revealed that MbWRKY1 was localized in the nucleus. The expression levels of MbWRKY1 were up-regulated by dehydration, salinity, and ABA treatments in M. baccata seedlings. When MbWRKY1 was introduced into tobacco, it improved drought stress tolerance in transgenic plants. Under the drought treatment, transgenic plants had higher contents of chlorophyll, proline, relative water, AsA, and GSH than wild-type (WT) plants. Compared with WT plants, the overexpression of MbWRKY1 in transgenic tobacco also led to decreased levels of H2O2, MDA, and elecrolyte leakage when dealing with drought stress. There were increased activities of POD, CAT, SOD, and APX in transgenic tobaccos, especially when dealing with drought treatment. Moreover, the MbWRKY1 transgenic plants enhanced the expressions of oxidative stress response (NtPOD, NtCAT, NtSOD, and NtAPX) and stress-related genes (NtP5CS and NtLEA5) when dealing with drought stress. These results suggest that the MbWRKY1 gene plays a positive regulatory role in drought stress response.

Metal trace elements, such as Fe, Zn, and Mn, are necessary micronutrients required by all plants. In this study, the MxNAS3 gene was cloned from Malus xiaojinensis and MxNAS3 was localized in the cytoplasmic membrane. The expression level of MxNAS3 in root and new leaf was higher than in mature leaf and phloem, which was greatly influenced by high and low Fe stresses, IAA and ABA treatments in M. xiaojinensis. Over-expression of MxNAS3 in transgenic Arabidopsis thaliana contributed to enhanced Fe stress tolerance, as well as higher levels of root length, fresh weight, concentrations of chlorophyll, nicotianamine, Fe, Zn, and Mn, especially under high and low Fe stresses. More importantly, it was the first time for us to find that higher expression of MxNAS3 in transgenic A. thaliana contributed to misshappen flowers. Moreover, the MxNAS5-OE A. thaliana had increased expression levels of flowering-related genes (AtYSL1, AtYSL3, AtAFDL, AtAP1, ATMYB21, and AtSAP).

Plant-specific WRKY transcription factors were involved in stress responses and ABA signaling. In the present study, a WRKY gene is isolated from Malus baccata (L.) Borkh and designated as MbWRKY3. Subcellular localization revealed that MbWRKY3 was localized onto nucleus. The MbWRKY3 expression levels were up-regulated by salinity, drought, and ABA treatments in M. baccata. When MbWRKY3 was introduced into tobaccos, it improved drought stress tolerance in transgenic plants. Compared to WT, the transgenic tobaccos had the higher levels of relative water content, and proline and chlorophyll contents, decreased levels of electrolyte leakage, MDA, and H2O2, increased activities of the reactive oxygen species-related enzymes (SOD, CAT, and POD), and greater up-regulations of the corresponding genes (NtSOD, NtCAT, and NtPOD), especially when dealt with drought stress. These results suggest that MbWRKY3 gene plays a positive regulatory role in drought stress response.

Plant-specific WRKY transcription factors are widely involved in abiotic stress responses. In this study, a WRKY gene was isolated from Malus baccata (L.) Borkh and designated it as MbWRKY2. Subcellular localization showed that MbWRKY2 was localized in the nucleus. The expression levels of MbWRKY2 were up-regulated by abiotic stresses in M. baccata. When MbWRKY2 was introduced into tobacco, it improved drought stress tolerance in transgenic plants. The transgenic tobaccos had the higher contents of chlorophyl, proline, relative water content, AsA, and GSH, increased activities of CAT, APX, SOD, and POD, and decreased levels of MDA, H2O2, and electrolyte leakage than wild-type, especially when dealt with dehydration treatment. Moreover, the MbWRKY2-OE plants enhanced the expression of oxidative stress response and stress-related genes involved in osmotic adjustment and membrane protection. These results suggest that MbWRKY2 gene plays a positive regulatory role in drought stress response.

Iron (Fe) is one of the essential micronutrients required by all plants. Citric acid is considered as the chelate substance in the long distance transport of Fe. In this study, a gene encoding putative citrate synthase was isolated from Malus xiaojinensis and designated as MxCS3. The MxCS3 gene encoded a protein of 235 amino acid residues with a theoretical isoelectric point of 9.47 and a predicted molecular mass of 26.3 kDa. Subcellular localization study revealed that MxCS3 is preferentially localized in mitochondrion and cytoplasmic membrane. The expression of MxCS3 was enriched in leaf, phloem, and root, which was highly affected by Fe stress, indoleacetic acid and abscisic acid treatment in M. xiaojinensis seedlings. When MxCS3 was transferred into Arabidopsis thaliana, it improved Fe stress tolerance in transgenic Arabidopsis. Increased expression of MxCS3 in transgenic A. thaliana also led to increased fresh weight, root length, CS activity, and the contents of chlorophyll, citrate acid, Fe and Zn, especially when dealt with Fe stress. More importantly, we firstly found that ectopic expression of MxCS3 resulted in abnormal flowers in transgenic Arabidopsis.

Cucumber is an important vegetable crop bearing fleshy pepo fruit harvested immature. Fruits left unpicked in time during summer production, as well as unfavorable environmental conditions during post-harvest shelf, will cause cucumber fruits to turn yellow and ripen, and thus impair the market value. Identification of maturity-related genes is of great agricultural and economic importance for cucumber production. Here, we isolated and characterized a MADS-box gene, Cucumis sativus SHATTERPROOF (CsSHP) in cucumber. Expression analysis indicated that CsSHP was specifically enriched in reproductive organs including stamens and carpels. Ectopic expression of CsSHP was unable to rescue the indehiscence silique phenotype of shp1 shp2 mutant plant in Arabidopsis. Instead, overexpression of CsSHP resulted in early flowering, precocious phenotypes, and capelloid organs in wild-type Arabidopsis. Biochemical analysis indicated that CsSHP directly interacted with cucumber SEPALLATA (SEP) proteins. CsSHP expression increased significantly during the yellowing stage of cucumber ripening, and was induced by exogenous application of abscisic acid (ABA). Therefore, CsSHP may participate in fruit maturation through the ABA pathway and floral organ specification via interaction with CsSEPs to form protein complex in cucumber.

Vegetable crops are major nutrient sources for humanity and have been well-cultivated since thousands of years of domestication. With the rapid development of next-generation sequencing and high-throughput genotyping technologies, the reference genome of more than 20 vegetables have been well-assembled and published. Resequencing approaches on large-scale germplasm resources have clarified the domestication and improvement of vegetable crops by human selection; its application on genetic mapping and quantitative trait locus analysis has led to the discovery of key genes and molecular markers linked to important traits in vegetables. Moreover, genome-based breeding has been utilized in many vegetable crops, including Solanaceae, Cucurbitaceae, Cruciferae, and other families, thereby promoting molecular breeding at a single-nucleotide level. Thus, genome-wide SNP markers have been widely used, and high-throughput genotyping techniques have become one of the most essential methods in vegetable breeding. With the popularization of gene editing technology research on vegetable crops, breeding efficiency can be rapidly increased, especially by combining the genomic and variomic information of vegetable crops. This review outlines the present genome-based breeding approaches used for major vegetable crops to provide insights into next-generation molecular breeding for the increasing global population.

Iron (Fe) is one of the essential micronutrients required by all plants. Nicotianamine (NA) is considered as the chelate substance in the transport of Fe. In the present study, a gene encoding putative nicotianamine synthase (NAS) is isolated from Malus xiaojinensis and designated as MxNAS2 . The MxNAS2 gene encodes a protein of 325 amino acid residues with a predicted molecular mass of 36.2 kDa and a theoretical isoelectric point of 5.18. Subcellular localization reveals that MxNAS2 is preferentially localized in vesicles and cytoplasmic membrane. The expression of MxNAS2 is more enriched in leaf, root, and phloem than xylem, which is highly affected by Fe stress and indoleacetic acid (IAA) treatment, whereas, weakly affected by abscisic acid (ABA) treatment in M. xiaojinensis seedlings. When MxNAS2 was introduced into tobacco, it promotes the synthesis of NAS and increases NA and chlorophyll contents. Overexpression of MxNAS2 improves the tolerance to Fe stress in transgenic tobacco, but leads to delayed flowering. Higher levels of MxNAS2 expression in transgenic tobacco contribute to misshapen flowers and increased levels of Fe, Mn, Cu and Zn in leaf and flower. In addition to its role in metal transport in plants, NA may be involved in the regulation of metal transfer within cells. These results suggest that NA excess influences the functions of metal-requiring proteins, including some of the transcription factors.

Iron (Fe) is one of the essential micronutrients required by all plants. Citric acid (CA) is considered as the chelate substance in the long distance transport of Fe. In the present study, a gene encoding putative citrate synthase (CS) was isolated from Malus domestica (L.) Borkh and designated as MdCS1. The MdCS1 gene encodes a protein of 473 amino acid residues with a theoretical isoelectric point of 7.72 and a predicted molecular mass of 52.7 kDa. Subcellular localization has revealed that MdCS1 is preferentially localized in cytoplasmic membrane. The expression of MdCS1 was enriched in leaf, root, and phloem, which was highly affected by Fe stress and indoleacetic acid treatment, while weakly by abscisic acid treatment in M. domestica seedlings. When MdCS1 was introduced into Arabidopsis, it promoted the synthesis of CS and increased CA content. Overexpression of MdCS1 improved the tolerance to Fe stress in transgenic Arabidopsis, but also led to increased fresh weight, CS activity, and contents of chlorophyll, CA and Fe, especially when dealt with Fe stress.

Iron is one of the essential micronutrients required by all plants and citric acid is considered to be the chelate substance in the long distance transport of iron. The expression of MxCS1 was enriched in active organs—leaf, root and phloem, which was strongly affected by Fe stress and IAA treatment, and weakly by ABA treatment in Malus xiaojinensis seedlings. This gene was introduced into the nongraminaceous plant tobacco, which promotes the synthesis of citrate synthase and increases the content of citric acid. Overexpression of MxCS1 improved Fe stress tolerance in transgenic tobacco and flowers presented morphological abnormalities. Increased expression of MxCS1 in transgenic tobacco plants also resulted in early-flowering and increased concentrations of Fe, Mn, Cu, and Zn in young leaves and flowers. In addition to its role in long-distance metal transport, citric acid may be involved in the regulation of metal transfer within cells. These results suggest that citric acid excess influenced the functions of metal-requiring proteins, including some transcription factors.

Iron (Fe) is one of the essential micronutrients required by all living organisms. Expression of MxNas1 of Malus xiaojinensis is enriched in active tissues, including leaves, roots, and phloem, and these seedlings are highly affected by Fe stress and indoleacetic acid treatment, but weakly affected by abscisic acid treatment. Subcellular localization has revealed that MxNas1 is preferentially localized in cell membranes. When this gene is introduced into tobacco, it promotes synthesis of nicotianamine (NA) synthase and increases NA content. Overexpression of MxNas1 improves tolerance to Fe stress in transgenic tobacco, but also leads to misshapen flowers. Higher levels of MxNas1 expression in transgenic tobacco plants also contributes to delayed flowering and increased levels of Fe and Zn in flowers. In addition to its role in metal transport in plants, NA may be involved in the regulation of metal transfer within cells. These results suggest that NA excess influences functions of metal-requiring proteins, including some of the transcription factors.

Apomixis is usually subdivided into parthenogenesis, apogamy, and apospory on the basis of different mechanisms of development and cytogenetic effects. Although most plants and animals undergo sexual reproduction to multiply, it is important to understand the role of apomixis in plant reproduction because of its useful applications in the breeding and propagation of some crops. Tetraploid Malus xiaojinensis Cheng et Jiang is a typical facultative apomictic plant species. Paternity and ploidy analyses of M. xiaojinensis seedlings were performed with flow cytometry in conjunction with microsatellite and single nucleotide polymorphism markers. The proportion of apomictic derived progeny of M. xiaojinensis ×Malus baccata was 54.05, 53.96, and 43.55 % from 2008 to 2010, respectively. The progeny of M. xiaojinensis × M. baccata comprised hybrids of 2x, 3x, 4x, or 5x ploidy, whereas apomictic offspring were 2x, 3x, or 4x. Among the apomictic derived progeny, the ploidy of restituted apomictic progeny was 2x, 3x, or 4x, whereas that of nonrestituted apomictic progeny was 4x only. The proportions of the different types of apomictic derived progeny differed among the years 2008 to 2010. The ploidy of progeny from emasculated flowers also segregated into 2x, 3x, and 4x individuals. These results indicate that both parthenogenesis and unreduced meiotic diplospory play important roles in apomictic reproduction in M. xiaojinensis.

Iron is one of the essential micronutrients required by all living organisms. In this study, we isolated a gene encoding putative citrate synthase (CS) from Malus xiaojinensis, designated as MxCS1. The MxCS1 gene encodes a protein of 473 amino acid residues with a predicted molecular mass of 52.5 kDa and a theoretical isoelectric point of 8.67. The expression of MxCS1 was enriched in the leaf rather than in phloem and root, however, its expression was hardly detected in the xylem. The gene expression was strongly induced by Fe stress treatment in the M. xiaojinensis seedlings. Over-expression of MxCS1 improved Fe deficiency tolerance in transgenic Arabidopsis. We argued that MxCS1 is a new member of the CS genes, and it may function as a regulator in response to iron stress in plants.

The effects of the heavy metal Cd in Malus xiaojinensis were investigated using hydroponic cultures. Chlorophyll and Fe concentrations in young leaves were markedly decreased by Cd treatment, although Fe concentration was significantly enhanced in the roots. A comparative examination of the Fe-deficiency responses due to Fe deficiency and Cd treatment was also performed. Both Fe deficiency and Cd treatment induced responses similar to those of Fe-deficiency in M. xiaojinensis, including acidification of the rhizosphere, enhanced Fe(III) chelate reductase activity, and upregulation of the Fe-deficiency-responsive genes MxIRT1 and MxFRO2-Like. However, the Fe-deficiency responses induced by Cd treatment were different in intensity and timing from those induced by Fe deficiency.