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Pollen coat proteins (PCPs) are cysteine-rich small-molecule proteins, which exhibit high levels of polymorphism and are expressed in gametocytes. Previous investigations have revealed that PCP genes are involved in pollen wall synthesis, pollen-stigma recognition, and pollen development and germination. However, gene expression and function of PCP family in pollen development is not well understood in Wucai (Brassica campestris L.). In this study, genome-wide identification and expression analysis of the BcPCP gene family members were conducted, including their physical and chemical properties, chromosome localization, phylogenetic relationships, gene structure, and tertiary structure. A total of 20 BcPCP genes were identified and classified into three subfamilies showing high homology to Arabidopsis thaliana. Expression pattern analysis indicated that the BcPCP gene family exhibits higher expression levels in reproductive organs, suggesting their potential involvement in the reproductive development. Notably, BraA02g002400.3 C, potentially associated with male sterility, was identified through multiple transcriptomic and proteomic datasets. Subsequently, sequence analysis revealed its homology with the Arabidopsis GRP20 gene, and thus it was named BcGRP20. Functional analysis of this gene showed that overexpression of BcGRP20 gene in the Arabidopsis grp20 mutant could restore anther fertility. Overall, our findings indicate that BcGRP20 plays a critical role in pollen development and may be the causative gene for male sterility in Wucai. This study provides candidate genes for further functional identification of BcPCP genes in Wucai, which are crucial for anther development. [ABSTRACT FROM AUTHOR]

Wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen) is a subspecies of Brassica campestris, is a kind of cold-tolerant vegetable widely cultivated in the Yangtze-Huai River Basin of China. To breed new varieties of resistance to stress, it is necessary to study the tolerance of Resistance to different stresses. Transcriptomic data showed that exogenous application of 2, 4-epbrassinolide (EBR) significantly increased the bHLH genes expression in wucai at low temperature, and bHLH57 was up regulated significantly. BHLH (Basic helix-loop-helix) TFs (transcription factor) is a superfamily of TFs with complex functions and related to various plant life activities. In this study, a total of 239 bHLH genes were identified, and their amino acid physicochemical properties, chromosome location, gene structure, phylogeny and cis-acting elements were analyzed by bioinformatics. Phylogenetic analysis showed that bHLH gene families in Brassica rapa and Arabidopsis were divided into six groups, and the distribution of bHLH genes in Brassica rapa was uneven. The BrbHLHs were irregularly mapped in the cultivated B. rapa genome. The maximum number (40) of BrbHLH genes were mapped on Chr09. In addition, there were tandem repeats in some genes. The collinearity analysis showed that 152 AtbHLH genes and 239 BrbHLH protein genes formed 296 collinearity pairs, and the Ka/Ks ratio ofall duplicated BrbHLH gene pairs had a Ka/Ks ratio of < < 1, indicating that the bHLH family genes may have undergone strong purification and selection during the evolution process. Cis-acting elements analysis showed that the promoter region of bHLH family genes in Brassica rapa had more responsive elements related to light, hormone and abiotic stress. The BcbHLH57 overexpressing Arabidopsis thaliana lines were subjected to different stress treatments, and the seed germination rate, root growth, survival rate and various plant physiological indexes were determined. The results showed that the transgenic lines were more tolerant to salt, heat and drought stress. In this study, the response of BcbHLH57 gene to salt, heat and drought stress was reported for the first time, which provided a basis for further research on the function of BcbHLH57 in abiotic stress. Key message: BcbHLH57 overexpressing Arabidopsis thaliana lines showed strong tolerance to salt, heat and drought stress, which provided a basis for further research on the function of BcbHLH57 in abiotic stress. [ABSTRACT FROM AUTHOR]

Chilling stress during the growing season could cause a series of changes in wucai (Brassica campestris L.). WS-1 (chilling-tolerant genotype) and Ta2 (chilling-sensitive genotype) were sampled in present study to explore the chilling tolerance mechanisms. Our results indicated that photosynthetic parameters exhibited lower level in Ta2 than in WS-1 under chilling stress. The rapid chlorophyll fluorescence dynamics curve showed that chilling resulted in a greater inactivation of photosystem II reaction center in Ta2. Reactive oxygen species and malondialdehyde content of chloroplast in Ta2 were higher than WS-1. The ascorbate–glutathione cycle in chloroplast of WS-1 played a more crucial role than Ta2, which was confirmed by higher activities of antioxidant enzymes including Ascorbate peroxidase, Glutathione reductase, Monodehydroascorbate reductase and Dehydroascorbate reductase and higher content of AsA and GSH. In addition, the ultrastructure of chloroplasts in Ta2 was more severely damaged. After low temperature stress, the shape of starch granules in Ta2 changed from elliptical to round and the volume became larger than that of WS-1. The thylakoid structure of Ta2 also became dispersed from the original tight arrangement. Combined with our previous study under heat stress, WS-1 can tolerant both chilling stress and heat stress, which was partly due to a stable photosynthetic system and the higher active antioxidant system in plants, in comparison to Ta2. [ABSTRACT FROM AUTHOR]

The novel male sterility line 12-14A of Wucai (Brassica campestris) was generated by backcrossing. In this study, morphological, molecular, and cytological analyses were performed to characterize this line. The phenotypes of flower organs of 12-14A were different from those of its maintainer line 12-14B, as the flowers of 12-14A were completely infertile. Molecular analysis confirmed that the male sterility line 12-14A was classified as the ogu CMS type. An analysis of anther development in the CMS line demonstrated that two types of abortion occur simultaneously: pollen mother cell abortion and tetrad-to-mononuclear microspore abortion. In addition, the mature anthers of 12-14A showed typical abortive features, such as appearing dry, shrunken, and scaly. A heterosis test of hybrids from CMS 12-14A and four inbred lines was carried out, and the F1 hybrids exhibited clear heterosis in plant weight, as well as in the protein, soluble sugar, and vitamin C content, suggesting high yields and high quality potential. These results indicate that this novel CMS line may have powerful potential in Wucai hybrid breeding. [ABSTRACT FROM AUTHOR]

Key message: We developed a novel Agrobacterium-mediated anther transformation for Wucai in planta, and in this procedure, the male germ line was the predominant target. Wucai (Brassica campestris L.), a variant of non-heading Chinese cabbage, is widely cultured in China and only improved by classic breeding methods. Here, a novel and efficient in planta Agrobacterium-mediated anther transformation method is developed based on the optimization of several factors that affect anther transformation. After optimization, transformation with the manual pollination application led to increased transient GUS expression in anthers (reaching 91.59%) and the transformation efficacies in planta (0.59–1.56% for four commercial cultivars). The stable integration and inheritance of the transgenes were further examined by molecular and genetic analyses. Three T2 transgenic lines presented a segregation ratio of 3:1, which was consistent with the Mendelian feature of a single dominant gene. In addition, the GUS histochemical assay and genetic crossing analysis revealed that the male germ line was the predominant target in this transformation. This optimized transformation system could provide a useful tool for both the improvement of cultivar qualities and investigation of functional genes in Wucai. [ABSTRACT FROM AUTHOR]

The objective of this study was to identify the effects of exogenous putrescine (Put) on leaf traits, hormones levels, and carbohydrate metabolism in cucumber seedlings under salt stress. The stress of 75 mM NaCl decreased plant growth and photosynthetic carboxylation efficiency. NaCl also increased the leaf thickness but destroyed the leaf internal structure. The contents of indoleacetic acid, zeatin, and zeatin riboside were decreased and the abscisic acid level was increased by NaCl. In addition, NaCl stress caused the accumulation of sucrose and starch in leaves and led to the feedback inhibition of photosynthesis, which can be inferred from the lower maximum rate of RuBisCo-mediated carboxylation ( V). The analysis of starch-metabolizing enzyme activities suggested that the largely improved amylopectin contents contributed to the starch accumulation. Put regulated the levels and ratios of endogenous hormones, lowered the leaf thickness, and protected the leaf structure from damage caused by NaCl. Furthermore, Put decreased the accumulation of sucrose and starch caused by NaCl in leaves through regulating the activities of enzymes involved in carbohydrate metabolism. In conclusion, Put regulates the hormones levels, leaf structure, and carbohydrate metabolism and therefore improves the photosynthesis and growth of NaCl-stressed cucumber plants. [ABSTRACT FROM AUTHOR]

Key message: This study focuses on the impact of carbohydrate metabolism and endogenous polyamines levels in leaves of cucumber seedlings under salt stress by exogenous BRs. Abstract: The effects of 24-epibrassinolide (EBL) on carbohydrate metabolism and endogenous content of polyamines were investigated in cucumber seedlings ( Cucumis sativus L. cv. Jinyou No. 4) exposed to salinity stress [80 mM Ca(NO)]. Spraying of exogenous EBL partially enhanced the enzyme activities of sucrose phosphate synthase, sucrose synthase and acid invertase; thus, raising the level of sucrose, fructose and total soluble sugars. The amylase activity was also increased by EBL, companied by the rising of sucrose level. These results indicated that EBL improved the carbohydrate metabolism of cucumber under Ca(NO) stress. Moreover, EBL raised the levels of soluble conjugated and insoluble bound polyamines while lowered the free polyamines content, particularly putrescine. Our experiment demonstrated that exogenous EBL elevated stability of cellular membrane and positively improve the carbohydrate metabolism in cucumber growing under Ca(NO) stress. [ABSTRACT FROM AUTHOR]

The effects of 0.1 μM 24-epibrassinolide (EBL) on plant growth (plant height, leaf area, fresh weight, and dry weight), chlorophyll content, photosynthetic characteristics, antioxidant enzymes, and chloroplast ultrastructure were investigated using cucumber seedlings ( Cucumis sativus L. cv. Jinyou No. 4) with 80 mM Ca(NO) to induce stress. The presence of Ca(NO) caused significant reductions in net photosynthetic rate ( P), stomatal conductance (Gs), intercellular CO concentration (Ci), and transpiration rate (Tr) of leaves. In addition, Ca(NO) markedly reduced the chlorophyll content and inhibited photochemical activity, including the actual photochemical efficiency (ΦPSII). In contrast, EBL increased the chlorophyll content, especially chlorophyll b, and minimized the harmful effects on photosynthesis caused by the Ca(NO). The application of EBL to the plants subjected to Ca(NO)-enhanced photochemical activity. EBL protected the photosynthetic membrane system from oxidative damage due to up-regulating the capacity of the antioxidant systems. Microscopic analyses revealed that Ca(NO) affected the structure of the photosynthetic apparatus and membrane system and induced damage of granal thylakoid layers, while EBL recovered the typical shape of chloroplasts and promoted the formation of grana. Taken together, EBL compensated for damage/losses by Ca(NO) due to the regulation of photosynthetic characteristics and the antioxidant system. [ABSTRACT FROM AUTHOR]

Hypoxia induces plant stress, particularly in cucumber plants under hydroponic culture. In plants, calcium is involved in stress signal transmission and growth. The ultimate goal of this study was to shed light on the mechanisms underlying the effects of exogenous calcium on the mitochondrial antioxidant system, the activity of respiratory metabolism enzymes, and ion transport in cucumber (Cucumis sativus L. cv. Jinchun No. 2) roots under hypoxic conditions. Our experiments revealed that exogenous calcium reduces the level of reactive oxygen species (ROS) and increases the activity of antioxidant enzymes in mitochondria under hypoxia. Exogenous calcium also enhances the accumulation of enzymes involved in glycolysis and the tricarboxylic acid (TCA) cycle. We utilized fluorescence and ultrastructural cytochemistry methods to observe that exogenous calcium increases the concentrations of Ca2+ and K+ in root cells by increasing the activity of plasma membrane (PM) H+-ATPase and tonoplast H+-ATPase and H+-PPase. Overall, our results suggest that hypoxic stress has an immediate and substantial effect on roots. Exogenous calcium improves metabolism and ion transport in cucumber roots, thereby increasing hypoxia tolerance in cucumber. [ABSTRACT FROM AUTHOR]