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Auxin transport is regulated by the AUX1/LAX, PIN, and ABCB gene families, controlling the distribution of auxin and ultimately fruit curving in cucumbers. However, studies on the differential expression of these auxin transporters and their roles in fruit curving are limited. In this study, we identified 36 auxin transporters from cucumber, including CsLAX1–7, CsPIN1–10, and CsABCB1–19. Basic characteristic analysis revealed that all CsLAX proteins were conservative, and a C-terminal NPNTY motif was found in CsPIN1–4/7–10. CsABCB1/5/11/14/17 were categorized as half-size transporters. Phylogenetic analysis revealed a genetic relationship between auxin transporters in Arabidopsis and cucumber. Exogenous auxin treatment on fruits and qPCR analysis indicated that differential expression patterns of auxin transporters control cucumber fruit curving. Co-expression analysis indicated that CsPIN1 and CsLAX2 were substantially negatively correlated, and they displayed opposite expression patterns in curved fruits. A proposed model suggested that CsLAX2 transports extracellular auxin to the convex side of the fruit; however, CsPIN1 inhibits auxin efflux at the same location. This leads to uneven auxin distribution that results in cucumber fruit curving. [ABSTRACT FROM AUTHOR]

The family of phosphatidylethanolamine-binding proteins (PEBPs) participates in various plant biological processes, mainly flowering regulation and seed germination. In cucurbit crops, several PEBP genes have been recognized to be responsible for flowering time. However, the investigation of PEBP family members across the genomes of cucurbit species has not been reported, and their conservation and divergence in structure and function remain largely unclear. Herein, PEBP genes were identified from seven cucurbit crops and were used to perform a comparative genomics analysis. The cucurbit PEBP proteins could be classified into MFT, FT, TFL, and PEBP clades, and further, the TFL clade was divided into BFT-like, CEN-like, and TFL1-like subclades. The MFT-like, FT-like, and TFL-like proteins were clearly distinguished by a critical amino acid residue at the 85th position of the Arabidopsis FT protein. In gene expression analysis, CsaPEBP1 was highly expressed in flowers, and its expression levels in females and males were 70.5 and 89.2 times higher, respectively, than those in leaves. CsaPEBP5, CsaPEBP6, and CsaPEBP7 were specifically expressed in male flowers, with expression levels 58.1, 17.3, and 15.7 times higher, respectively, than those of leaves. At least five CsaPEBP genes exhibited the highest expression during the later stages of corolla opening. Through clustering of time-series-based RNA-seq data, several potential transcription factors (TFs) interacting with four CsaPEBPs were identified during cucumber corolla opening. Because of the tandem repeats of binding sites in promoters, NF-YB (Csa4G037610) and GATA (Csa7G64580) TFs appeared to be better able to regulate the CsaPEBP2 and CsaPEBP5 genes, respectively. This study would provide helpful information for further investigating the roles of PEBP genes and their interacting TFs in growth and development processes, such as flowering time regulation in cucurbit crops. [ABSTRACT FROM AUTHOR]

Fructokinase (FRK) and fructokinase-like (FLN), belonging to the phosphofructokinase B type subfamily, share substantial sequence similarity, and are crucial in various plant physiological processes. However, there is limited information regarding what functionally differentiates plant FRKs from FLNs. Here, a total of three CsFRKs and two CsFLNs were identified from the cucumber genome. Their significant difference lay in the structure of their G/AXGD motif, which existed as GAGD in CsFRKs, but as G/ASGD in CsFLNs. Comparative phylogenetic analysis classified CsFRKs and CsFLNs into five sub-branches consistent with their quite different exon/intron organizations. Both transcriptome data and RT-qPCR analyses revealed that CsFRK3 was the most active gene, with the highest expression in the majority of tissues tested. Moreover, the expression levels of two putative plastidic genes, CsFRK1 and CsFLN2, were significantly positively associated with chlorophyll accumulation in the chlorophyll-reduced cucumber mutant. Briefly, both CsFRK and CsFLN genes were involved in the development of sink tissues, especially CsFRK3. CsFRK1 and CsFLN2 were recognized as candidates in the chlorophyll biosynthesis pathway of cucumber. These results would greatly assist in further investigation on functional characterization of FRKs and FLNs, especially in the development and chlorophyll biosynthesis of cucumber. [ABSTRACT FROM AUTHOR]

Propamocarb is a pesticide widely used to control cucumber downy mildew. The overuse of propamocarb has resulted in residues and phytotoxicity. However, the detoxification and metabolic process of propamocarb have not been documented well. Our previous work showed differences in the propamocarb residues among the different genotypes of cucumber and their regulation by multiple genes. Based on the already reported data on gene expression profiles under propamocarb treatment, we identified the glutathione pathway, including six different genes (Csa4M303130, Csa3M133380, Csa5M409710, Csa7M395820, Csa3M597320, and Csa1M571280), involved in propamocarb detoxification. The qPCR analysis showed that Csa1M571280 (CsGSH2) was most significantly and differentially expressed at 48 h after propamocarb spray in the cucumber varieties Y3F604 (low propamocarb residues) and M729 (high propamocarb residues). In Y3F604, CsGSH2 expression increased from 6 to 48 h after spraying propamocarb, and the expression was positively correlated with propamocarb residues, whereas M729 showed no significant difference in CsGSH2 expression. Therefore, we presumed CsGSH2 as a key gene in managing propamocarb residues. Gene functional analysis showed that propamocarb residues decreased in CsGSH2-overexpressing plants and increased in CsGSH2-antisense plants. Overexpression of CsGSH2 enhanced glutathione (GSH) accumulation and glutathione S-transferase (GST), glutathione reductase (GR), and glutathione peroxidase (GPX) activities, probably for propamocarb detoxification. The activity of antioxidant enzymes (SOD, POD, CAT, and APX) increased to maintain a high antioxidant capacity in CsGSH2-overexpressing plants. The superoxide (O2−), hydrogen peroxide (H2O2), and malondialdehyde (MDA) levels decreased in CsGSH2-overexpressing plants, promoting the antioxidant system composed of ascorbic acid and glutathione (AsA-GSH). Thus, we conclude that CsGSH2 alleviates propamocarb residues and phytotoxicity by enhancing cucumber's antioxidant and glutathione detoxification potential. [ABSTRACT FROM AUTHOR]

Basic leucine zipper (bZIP) transcription factors play crucial roles in various abiotic stress responses as well as anthocyanin accumulation. Anthocyanins are most abundant in colorful skin radish, which exhibit strong antioxidant activity that offers benefits for human health. Here, a total of 135 bZIP-encoding genes were identified from radish genome. Synteny analysis showed that 104 radish and 63 ArabidopsisbZIP genes were orthologous. Transcriptome analysis revealed that 10 RsbZIP genes exhibited high-expression levels in radish taproot (RPKM>10). Specifically, RsbZIP010 exhibited down-regulated expression under Cd, Cr and Pb stresses, whereas RsbZIP031 and RsbZIP059 showed significant down-regulation under heat and salt stresses, respectively. RT-qPCR analysis indicated that RsbZIP011 and RsbZIP102 were significantly up-regulated in the tissues of radish with high anthocyanin contents. Furthermore, the promoter sequences of 39 anthocyanin-related genes were found to contain G-box or ACE-box elements that could be recognized by bZIP family members. Taken together, several RsbZIPs might be served as critical regulators in radish taproot under Cd, Cr, Pb, heat and salt stresses. RsbZIP011 and RsbZIP102 were the potential participants in anthocyanin biosynthesis pathway of radish. These results facilitate further investigation on functional characterization of bZIP genes in response to abiotic stress and anthocyanin biosynthesis in radish. [ABSTRACT FROM AUTHOR]