Comparing the differences in quality profiles and antioxidant activity in seven pumpkin cultivars (Cucurbita moschata and Cucurbita maxima) at harvest and during postharvest storage.

Pumpkin, nutritious vegetable, is renowned for its extended shelf life. In this study, seven pumpkin cultivars from Cucurbita moschata and Cucurbita maxima were comparatively characterized for 25 physiochemical quality factors, starch granule structures, antioxidant activity, and correlations at 0-60 days of postharvest (dop). The findings revealed that sucrose and carotenoid contents increased in C. moschata, while they initially increased and then decreased in C. maxima. Additionally, acidity, primarily driven by malic acid, decreased in C. maxima but increased in C. maxima. The starch content of C. moschata and C. maxima reached its maximum value at 30 dop and 20 dop, respectively. The DPPH radical scavenging activity correlated with the carotenoid content in both pumpkin species. Conclusively, C. moschata demonstrated improved nutritional and quality at 20-30 dop, while C. maxima exhibited higher commercial suitability at 10-20 dop. The findings suggested that pumpkin storage was crucial for quality improvement.

The CsTM alters multicellular trichome morphology and enhances resistance against aphid by interacting with CsTIP1;1 in cucumber.

The multicellular trichomes of cucumber (Cucumis sativus L.) serve as the primary defense barrier against external factors, whose impact extends beyond plant growth and development to include commercial characteristics of fruits. The aphid (Aphis gossypii Glover) is one of prominent pests in cucumber cultivation. However, the relationship between physical properties of trichomes and the aphid resistance at molecular level remains largely unexplored. Here, a spontaneous mutant trichome morphology (tm) was characterized by increased susceptibility towards aphid. Further observations showed the tm exhibited a higher and narrower trichome base, which was significantly distinguishable from that in wild-type (WT). We conducted map-based cloning and identified the candidate, CsTM, encoding a C-lectin receptor-like kinase. The knockout mutant demonstrated the role of CsTM in trichome morphogenesis. The presence of SNP does not regulate the relative expression of CsTM, but diminishes the CsTM abundance of membrane proteins in tm. Interestingly, CsTM was found to interact with CsTIP1;1, which encodes an aquaporin with extensive reports in plant resistance and growth development. The subsequent aphid resistance experiments revealed that both CsTM and CsTIP1;1 regulated the development of trichomes and conferred resistance against aphid by affecting cytoplasmic H2O2 contents. Transcriptome analysis revealed a significant enrichment of genes associated with pathogenesis, calcium binding and cellulose synthase. Overall, our study elucidates an unidentified mechanism that CsTM-CsTIP1;1 alters multicellular trichome morphology and enhances resistance against aphid, thus providing a wholly new perspective for trichome morphogenesis in cucumber.

Niche differentiation and biogeography of Bathyarchaeia in paddy soil ecosystems: a case study in eastern China.

Bathyarchaeia (formerly Bathyarchaeota) is a group of highly abundant archaeal communities that play important roles in global biogeochemical cycling. Bathyarchaeia is predominantly found in sediments and hot springs. However, their presence in arable soils is relatively limited. In this study, we aimed to investigate the spatial distributions and diversity of Bathyarchaeia in paddy soils across eastern China, which is a major rice production region. The relative abundance of Bathyarchaeia among total archaea ranged from 3 to 68% in paddy soils, and Bathy-6 was the dominant subgroup among the Bathyarchaeia (70-80% of all sequences). Bathyarchaeia showed higher migration ability and wider niche width based on the neutral and null model simulations. Bathy-6 was primarily assembled by deterministic processes. Soil pH and C/N ratio were identified as key factors influencing the Bathyarchaeia composition, whereas C/N ratio and mean annual temperature influenced the relative abundance of Bathyarchaeia. Network analysis showed that specific Bathyarchaeia taxa occupied keystone positions in the archaeal community and co-occurred with some methanogenic archaea, including Methanosarcina and Methanobacteria, and ammonia-oxidizing archaea belonging to Nitrososphaeria. This study provides important insights into the biogeography and niche differentiation of Bathyarchaeia particularly in paddy soil ecosystems.

Transcriptomic analysis reveals the molecular basis of photoperiod-regulated sex differentiation in tropical pumpkins (Cucurbita moschata Duch.).

BACKGROUND: Photoperiod, or the length of the day, has a significant impact on the flowering and sex differentiation of photoperiod-sensitive crops. The "miben" pumpkin (the main type of Cucurbita moschata Duch.) is well-known for its high yield and strong disease resistance. However, its cultivation has been limited due to its sensitivity to photoperiod. This sensitivity imposes challenges on its widespread cultivation and may result in suboptimal yields in regions with specific daylength conditions. As a consequence, efforts are being made to explore potential strategies or breeding techniques to enhance its adaptability to a broader range of photoperiods, thus unlocking its full cultivation potential and further promoting its valuable traits in agriculture. RESULTS: This study aimed to identify photoperiod-insensitive germplasm exhibiting no difference in sex differentiation under different day-length conditions. The investigation involved a phenotypic analysis of photoperiod-sensitive (PPS) and photoperiod-insensitive (PPIS) pumpkin materials exposed to different day lengths, including long days (LDs) and short days (SDs). The results revealed that female flower differentiation was significantly inhibited in PPS_LD, while no differences were observed in the other three groups (PPS_SD, PPIS_LD, and PPIS_SD). Transcriptome analysis was carried out for these four groups to explore the main-effect genes of sex differentiation responsive to photoperiod. The main-effect gene subclusters were identified based on the principal component and hierarchical cluster analyses. Further, functional annotations and enrichment analysis revealed significant upregulation of photoreceptors (CmCRY1, F-box/kelch-repeat protein), circadian rhythm-related genes (CmGI, CmPRR9, etc.), and CONSTANS (CO) in PPS_LD. Conversely, a significant downregulation was observed in most Nuclear Factor Y (NF-Y) transcription factors. Regarding the gibberellic acid (GA) signal transduction pathway, positive regulators of GA signaling (CmSCL3, CmSCL13, and so forth) displayed higher expression levels, while the negative regulators of GA signaling, CmGAI, exhibited lower expression levels in PPS_LD. Notably, this effect was not observed in the synthetic pathway genes. Furthermore, genes associated with ethylene synthesis and signal transduction (CmACO3, CmACO1, CmERF118, CmERF118-like1,2, CmWIN1-like, and CmRAP2-7-like) showed significant downregulation. CONCLUSIONS: This study offered a crucial theoretical and genetic basis for understanding how photoperiod influences the mechanism of female flower differentiation in pumpkins.

Global biogeographic distribution of Bathyarchaeota in paddy soils.

Bathyarchaeota, known as key participants of global elements cycling, is highly abundant and diverse in the sedimentary environments. Bathyarchaeota has been the research spotlight on sedimentary microbiology; however, its distribution in arable soils is far from understanding. Paddy soil is a habitat similar to freshwater sediments, while the distribution and composition of Bathyarchaeota in paddy soils have largely been overlooked. In this study, we collected 342 in situ paddy soil sequencing data worldwide to illuminate the distribution patterns of Bathyarchaeota and explore their potential ecological functions in paddy soils. The results showed that Bathyarchaeota is the dominant archaeal lineage, and Bathy-6 is the most predominant subgroup in paddy soils. Based on random forest analysis and construction of a multivariate regression tree, the mean annual precipitation and mean annual temperature are identified as the factors significantly influencing the abundance and composition of Bathyarchaeota in paddy soils. Bathy-6 was abundant in temperate environments, while other subgroups were more abundant in sites with higher rainfall. There are highly frequent associations between Bathyarchaeota and methanogens and ammonia-oxidizing archaea. The interactions between Bathyarchaeota and microorganisms involved in carbon and nitrogen metabolism imply a potential syntrophy between these microorganisms, suggesting that members of Bathyarchaeota could be important participants of geochemical cycle in paddy soils. These results shed light on the ecological lifestyle of Bathyarchaeota in paddy soils, and provide some baseline for further understanding Bathyarchaeota in arable soils. IMPORTANCE Bathyarchaeota, the dominant archaeal lineage in sedimentary environments, has been the spotlight of microbial research due to its vital role in carbon cycling. Although Bathyarchaeota has been also detected in paddy soils worldwide, its distribution in this environment has not yet been investigated. In this study, we conducted a global scale meta-analysis and found that Bathyarchaeota is also the dominant archaeal lineage in paddy soils with significant regional abundance differences. Bathy-6 is the most predominant subgroup in paddy soils, which differs from sediments. Furthermore, Bathyarchaeota are highly associated with methanogens and ammonia-oxidizing archaea, suggesting that they may be involved in the carbon and nitrogen cycle in paddy soil. These interactions provide insight into the ecological functions of Bathyarchaeota in paddy soils, which will be the foundation of future studies regarding the geochemical cycle in arable soils and global climate change.

A time-course transcriptome analysis of wax gourd fruit development reveals predominant genes regulating taste and nutrition.

Wax gourd, which belongs to Cucurbitaceae, is an excellent plant resource with the concomitant function of both medicine and foodstuff. Its unique taste and rich nutrition are deeply accepted by consumers. However, the main flavor and nutrients are still unclear, which restricts the quality breeding process of wax gourd. Here, we discovered that monosaccharides, malic acid and citrulline affect the flavor and nutrition of wax gourd and clarified the dynamic accumulation process of these metabolites. To gain insights into the underlying predominant genes regulating accumulation of these metabolites, we performed a time-course transcriptome analysis using RNA-sequencing analysis and compared the expression of screened genes among twenty-four germplasms with different metabolites levels. In addition, the expression abundance among the homologous genes were also analyzed. Finally, a total of 8 genes related to sugar [AGA2 (Bhi03G001926), SUS (Bhi12G001032)], malic acid [MDH (Bhi12G001426, Bhi01G000427), PEPC (Bhi12G000721, Bhi09G002867), ME (Bhi01G002616)] and citrulline [ASS (Bhi02G000401)], respectively were determined. In summary, understanding the core genes influencing taste or nutrition will provide a theoretical basis for fruit quality improvement in wax gourd.

Transcriptomic and functional analysis provides molecular insights into multicellular trichome development.

Trichomes, the hair-like structures located on aerial parts of most vascular plants, are associated with a wide array of biological processes and affect the economic value of certain species. The processes involved in unicellular trichome formation have been well-studied in Arabidopsis (Arabidopsis thaliana). However, our understanding of the morphological changes and the underlying molecular processes involved in multicellular trichome development is limited. Here, we studied the dynamic developmental processes involved in glandular and nonglandular multicellular trichome formation in cucumber (Cucumis sativus L.) and divided these processes into five sequential stages. To gain insights into the underlying mechanisms of multicellular trichome formation, we performed a time-course transcriptome analysis using RNA-sequencing analysis. A total of 711 multicellular trichome-related genes were screened and a model for multicellular trichome formation was developed. The transcriptome and co-expression datasets were validated by reverse transcription-quantitative PCR and in situ hybridization. In addition, virus-induced gene silencing analysis revealed that CsHOMEOBOX3 (CsHOX3) and CsbHLH1 are involved in nonglandular trichome elongation and glandular trichome formation, respectively, which corresponds with the transcriptome data. This study presents a transcriptome atlas that provides insights into the molecular processes involved in multicellular trichome formation in cucumber and can be an important resource for future functional studies.

Bacterial agents affected bacterial community structure to mitigate greenhouse gas emissions during sewage sludge composting.

The present work studied the influence of bacterial agents (B1, B2) and bamboo biochar (BB) on greenhouse gas emissions and bacterial community during the sewage sludge composting. Results showed that compared with CK, the total methane emissions ofC, B1, B1C, B2, and B2C treatments declined by 16.4%, 25.2%, 45.4%, 7.8%, and 44.4%, respectively. The total N2O emissions ofC and B1C treatments declined by 5.1% and 3.7% while B1, B2, and B2C treatments increased the total N2O emissions by 6.7%, 21.6%, and 10.4%, respectively. These results illustrated that the addition of BB is conducive for reducing greenhouse gas emissions while different bacterial agents have various effects. According to pearson correlation analysis, N2O emissions and Acidimicrobiia, Alphaproteobacteria, Gammaproteobacteria, and Tepidiformia have strong negative correlation while positive correlation with Bacilli and Clostridia. Methane emissions have a strong negative correlation with Actinobacteria. CO2 emissions have a strong positive correlation with Bacilli.

Characterization of Starch in Cucurbita moschata Germplasms throughout Fruit Development.

Pumpkins (Cucurbita moschata; Cucurbitaceae) are the rich source of nutrients and valued for their biologically active substances to be used for the treatment of several diseases. The contents, composition, and conformation of starch are the significant quality traits of C. moschata. Two germplasms were targeted for analysis regarding the taste difference. Results indicated that the total starch contents and amylose/amylopectin ratio were high in CMO-X as compared to CMO-E during each fruit development stage. Scanning electron microscopy and transmission electron microscopy observations revealed that smooth surface starch granules fused together to enhance the starch accumulation. For a comparison of fruit development in CMO-E and CMO-X, the putative pathway for starch metabolism was developed and homologs were identified for each key gene involved in the pathway. GBSS and SBE were correlated with the difference in the amylose/amylopectin ratio of CMO-E and CMO-X. Conclusively, the developmental regulation of genes associated with starch accumulation can be considered as an important factor for the determination of fruit quality.

Metabolic and transcriptomic analysis of two Cucurbita moschata germplasms throughout fruit development.

BACKGROUND: Pumpkins (Cucurbita moschata; Cucurbitaceae) are valued for their fruits and seeds and are rich in nutrients. Carotenoids and sugar contents, as main feature of pumpkin pulp, are used to determine the fruit quality. RESULTS: Two pumpkin germplasms, CMO-X and CMO-E, were analyzed regarding the essential quality traits such as dry weight, soluble solids, organic acids, carotenoids and sugar contents. For the comparison of fruit development in these two germplasms, fruit transcriptome was analyzed at 5 different developmental stages from 0 d to 40 d in a time course manner. Putative pathways for carotenoids biosynthesis and sucrose metabolism were developed in C. moschata fruit and homologs were identified for each key gene involved in the pathways. Gene expression data was found consistent with the accumulation of metabolites across developmental stages and also between two germplasms. PSY, PDS, ZEP, CRTISO and SUS, SPS, HK, FK were found highly correlated with the accumulation of carotenoids and sucrose metabolites, respectively, at different growth stages of C. moschata as shown by whole transcriptomic analysis. The results of qRT-PCR analysis further confirmed the association of these genes. CONCLUSION: Developmental regulation of the genes associated with the metabolite accumulation can be considered as an important factor for the determination of C. moschata fruit quality. This research will facilitate the investigation of metabolic profiles in other cultivars.

Selection footprints reflect genomic changes associated with breeding efforts in 56 cucumber inbred lines.

Cucumber selective breeding over recent decades has dramatically increased productivity and quality, but the genomic characterizations and changes associated with this breeding history remain unclear. Here, we analyzed the genome resequencing data of 56 artificially selected cucumber inbred lines that exhibit various phenotypes to detect trait-associated sequence variations that reflect breeding improvement. We found that the 56 cucumber lines could be assigned to group 1 and group 2, and the two groups formed a distinctive genetic structure due to the breeding history involving hybridization and selection. Differentially selected regions were identified between group 1 and group 2, with implications for genomic-selection breeding signatures. These regions included known quantitative trait loci or genes that were reported to be associated with agronomic traits. Our results advance knowledge of cucumber genomics, and the 56 selected inbred lines could be good germplasm resources for breeding.

Effects of Total Dissolved Gas Supersaturation in Fish of Different Sizes and Species.

Two endemic fish in the upper Yangtze River, the Rock Carp (Procypris rabaudi) and Prenant's Schizothoracin (Schizothorax prenanti), were used as research objects in this study to assess the effects of total dissolved gas (TDG) supersaturation on fish of varying sizes. Fish were exposed to TDG-supersaturated water at the levels of 145, 140, 135, 130, and 125%. The results showed that fish swam slowly, responded clumsily, and then exhibited spiral swimming performance after a period of exposure to TDG-supersaturated water. Fish exhibited exophthalmos, body swelling, gill bleeding, and caudal fin bleeding when they died in the TDG-supersaturated water. With the increase in TDG supersaturation, the tolerance capacity of fish to supersaturated TDG significantly reduced. At high supersaturation, the difference in survival time between species was not significant, while fish with smaller sizes showed greater tolerance capacity. At low supersaturation, the tolerance capacity of fish was mainly affected by species, and the influence of size was relatively small. With the decrease in TDG supersaturation, the catalase (CAT) activity first increased and then decreased. Rock Carp displayed significantly less activity than Prenant's Schizothoracin on exposure to TDG-supersaturated water. At high supersaturation levels, the CAT activity of Prenant's Schizothoracin of small size was greater than that of large Prenant's Schizothoracin. In contrast, small Prenant's Schizothoracin showed less CAT activity at low TDG levels than did large individuals.

The Tolerance Characteristics of Resident Fish in the Upper Yangtze River under Varying Gas Supersaturation.

In circumstances where total dissolved gas (TDG) levels are variable, the peak TDG and duration are expected to be the dominant drivers of fish survival. Focusing on the peak TDG and duration in natural rivers, a laboratory experiment and field experiments in the upper Yangtze River were conducted with Prenant's Schizothoracin (Schizothorax prenanti), a rare species inhabiting the upper Yangtze River, to examine the tolerance characteristics of fish under varying gas supersaturation levels. The results of the field experiments showed that TDG supersaturation in natural rivers changed greatly during the flood period due to reservoir regulation. The survival of fish was affected by TDG levels, water depth and TDG fluctuation range. A high TDG level, and shallow compensatory water depth caused fish mortality in the field experiment to be higher in September than in July. The results of the laboratory experiment showed that fish tolerance was lower under fluctuating TDG supersaturation than under constant TDG supersaturation. The tolerance of fish to TDG supersaturation varied depending on peak TDG and duration. Under the fluctuation range of 115-125%, fish survival in the 6 h-6 h cycle was significantly different from that in the 8 h-8 h cycle. The fluctuation cycle did not affect fish survival at the fluctuation range of 110-130%. Intermittent lower TDG supersaturation does not significantly increase the tolerance of fish. This study revealed the tolerance characteristics of resident fish in the upper Yangtze River to TDG supersaturation, which provides a reference to the ecological operation of reservoirs and may contribute to the protection of aquatic organisms.

A CsTu-TS1 regulatory module promotes fruit tubercule formation in cucumber.

The fruit epidermal features such as the size of tubercules are important fruit quality traits for cucumber production. But the mechanisms underlying tubercule formation remain elusive. Here, tubercule size locus CsTS1 was identified by map-based cloning and was found to encode an oleosin protein. Allelic variation was identified in the promoter region of CsTS1, resulting in low expression of CsTS1 in all 22 different small-warty or nonwarty cucumber lines. High CsTS1 expression levels were closely correlated with increased fruit tubercule size among 44 different cucumber lines. Transgenic complementation and RNAi-mediated gene silencing of CsTS1 in transgenic cucumber plants demonstrated that CsTS1 positively regulates the development of tubercules. CsTS1 is highly expressed in the peel at fruit tubercule forming and enlargement stage. Auxin content and expression of three auxin signalling pathway genes were altered in the 35S:CsTS1 and CsTS1-RNAi fruit tubercules, a result that was supported by comparing the cell size of the control and transgenic fruit tubercules. CsTu, a C2 H2 zinc finger domain transcription factor that regulates tubercule initiation, binds directly to the CsTS1 promoter and promotes its expression. Taken together, our results reveal a novel mechanism in which the CsTu-TS1 complex promotes fruit tubercule formation in cucumber.

Classification of fruit trichomes in cucumber and effects of plant hormones on type II fruit trichome development.

MAIN CONCLUSION: Cucumber fruit trichomes could be classified into eight types; all of them are multicellular with complex and different developmental processes as compared with unicellular trichomes in other plants. The fruit trichomes or fruit spines of cucumber, Cucumis sativus L., are highly specialized structures originating from epidermal cells with diverse morphology, which grow perpendicular to the fruit surface. To understand the underlying molecular mechanisms of fruit trichome development, in this study, we conducted morphological characterization and classification of cucumber fruit trichomes and their developmental processes. We examined the fruit trichomes among 200 cucumber varieties, which could be classified into eight morphologically distinct types (I-VIII). Investigation of the organogenesis of the eight types of trichomes revealed two main developmental patterns. The development of glandular trichomes had multiple stages including initiation and expansion of the trichome precursor cell protuberating out of the epidermal surface, followed by periclinal bipartition to two cells (top and bottom) which later formed the head region and the stalk, respectively, through subsequent cell divisions. The non-glandular trichome development started with the expansion of the precursor cell perpendicularly to the epidermal plane followed by cell periclinal division to form a stalk comprising of some rectangle cells and a pointed apex cell. The base cell then started anticlinal bipartition to two cells, which then underwent many cell divisions to form a multicellular spherical structure. In addition, phytohormones as environmental cues were closely related to trichome development. We found that GA and BAP were capable of increasing trichome number per fruit with distinct effects under different concentrations.

Comprehensive analysis of NAC transcription factors and their expression during fruit spine development in cucumber (Cucumis sativus L.).

The cucumber (Cucumis sativus L.) is an important vegetable crop worldwide, and fruit trichomes or spines are an important trait for external fruit quality. The mechanisms underlying spine formation are not well understood, but the plant-specific NAC family of transcription factors may play important roles in fruit spine initiation and development. In this study, we conducted a genome-wide survey and identified 91 NAC gene homologs in the cucumber genome. Clustering analysis classified these genes into six subfamilies; each contained a varying number of NAC family members with a similar intron-exon structure and conserved motifs. Quantitative real-time PCR analysis revealed tissue-specific expression patterns of these genes, including 10 and 12 that exhibited preferential expression in the stem and fruit, respectively. Thirteen of the 91 NAC genes showed higher expression in the wild-type plant than in its near-isogenic trichome mutant, suggesting their important roles in fruit spine development. Exogenous application of four plant hormones promoted spine formation and increased spine density on the cucumber fruits; several NAC genes showed differential expression over time in response to phytohormone treatments on cucumber fruit, implying their essential roles in fruit-trichome development. Among the NAC genes identified, 12 were found to be targets of 13 known cucumber micro-RNAs. Collectively, these findings provide a useful resource for further analysis of the interactions between NAC genes and genes underlying trichome organogenesis and development during fruit spine development in cucumber.

Cucumber (Cucumis sativus L.) Nitric Oxide Synthase Associated Gene1 (CsNOA1) Plays a Role in Chilling Stress.

Nitric oxide (NO) is a gaseous signaling molecule in plants, transducing information as a result of exposure to low temperatures. However, the underlying molecular mechanism linking NO with chilling stress is not well understood. Here, we functionally characterized the cucumber (Cucumis sativus L.) nitric oxide synthase-associated gene, NITRIC OXIDE ASSOCIATED 1 (CsNOA1). Expression analysis of CsNOA1, using quantitative real-time PCR, in situ hybridization, and a promoter::ß-glucuronidase (GUS) reporter assay, revealed that it is expressed mainly in the root and shoot apical meristem (SAM), and that expression is up-regulated by low temperatures. A CsNOA1-GFP fusion protein was found to be localized in the mitochondria, and ectopic expression of CsNOA1 in the A. thaliana noa1 mutant partially rescued the normal phenotype. When overexpressing CsNOA1 in the Atnoa1 mutant under normal condition, no obvious phenotypic differences was observed between its wild type and transgenic plants. However, the leaves from mutant plant grown under chilling conditions showed hydrophanous spots and wilting. Physiology tolerance markers, chlorophyll fluorescence parameter (Fv/Fm), and electrolyte leakage, were observed to dramatically change, compared mutant to overexpressing lines. Transgenic cucumber plants revealed that the gene is required by seedlings to tolerate chilling stress: constitutive over-expression of CsNOA1 led to a greater accumulation of soluble sugars, starch, and an up-regulation of Cold-regulatory C-repeat binding factor3 (CBF3) expression as well as a lower chilling damage index (CI). Conversely, suppression of CsNOA1 expression resulted in the opposite phenotype and a reduced NO content compared to wild type plants. Those results suggest that CsNOA1 regulates cucumber seedlings chilling tolerance. Additionally, under normal condition, we took several classic inhibitors to perform, and detect endogenous NO levels in wild type cucumber seedling. The results suggest that generation of endogenous NO in cucumber leaves occurs largely independently in the (CsNOA1) and nitrate reductase (NR) pathway.

The Infection of Cucumber (Cucumis sativus L.) Roots by Meloidogyne incognita Alters the Expression of Actin-Depolymerizing Factor (ADF) Genes, Particularly in Association with Giant Cell Formation.

Cucumber (Cucumis sativus L.) is threatened by substantial yield losses due to the south root-knot nematode (Meloidogyne incognita). However, understanding of the molecular mechanisms underlying the process of nematode infection is still limited. In this study, we found that M. incognita infection affected the structure of cells in cucumber roots and treatment of the cytoskeleton inhibitor (cytochalasin D) reduced root-knot nematode (RKN) parasitism. It is known that Actin-Depolymerizing Factor (ADF) affects cell structure, as well as the organization of the cytoskeleton. To address the hypothesis that nematode-induced abnormal cell structures and cytoskeletal rearrangements might be mediated by the ADF genes, we identified and characterized eight cucumber ADF (CsADF) genes. Phylogenetic analysis showed that the cucumber ADF gene family is grouped into four ancient subclasses. Expression analysis revealed that CsADF1, CsADF2-1, CsADF2-2, CsADF2-3 (Subclass I), and CsADF6 (Subclass III) have higher transcript levels than CsADF7-1, CsADF7-2 (Subclass II genes), and CsADF5 (Subclass IV) in roots. Members of subclass I genes (CsADF1, CsADF2-1, CsADF2-2, and CsADF2-3), with the exception of CsADF2-1, exhibited a induction of expression in roots 14 days after their inoculation (DAI) with nematodes. However, the expression of subclass II genes (CsADF7-1 and CsADF7-2) showed no significant change after inoculation. The transcript levels of CsADF6 (Subclass III) showed a specific induction at 21 DAI, while CsADF5 (Subclass IV) was weakly expressed in roots, but was strongly up-regulated as early as 7 DAI. In addition, treatment of roots with cytochalasin D caused an approximately 2-fold down-regulation of the CsADF genes in the treated plants. These results suggest that CsADF gene mediated actin dynamics are associated with structural changes in roots as a consequence of M. incognita infection.

The WD-Repeat Protein CsTTG1 Regulates Fruit Wart Formation through Interaction with the Homeodomain-Leucine Zipper I Protein Mict.

The cucumber (Cucumis sativus) fruit is covered with bloom trichomes and warts (composed of spines and tubercules), which have an important impact on the commercial value of the crop. However, little is known about the regulatory mechanism underlying their formation. Here, we reported that the cucumber WD-repeat homolog CsTTG1, which is localized in the nucleus and cytomembrane, plays an important role in the formation of cucumber fruit bloom trichomes and warts. Functional characterization of CsTTG1 revealed that it is mainly expressed in the epidermis of cucumber ovary and that its overexpression in cucumber alters the density of fruit bloom trichomes and spines, thereby promoting the warty fruit trait. Conversely, silencing CsTTG1 expression inhibits the initiation of fruit spines. Molecular and genetic analyses showed that CsTTG1 acts in parallel to Mict/CsGL1, a key trichome formation factor, to regulate the initiation of fruit trichomes, including fruit bloom trichomes and spines, and that the further differentiation of fruit spines and formation of tubercules regulated by CsTTG1 is dependent on Mict Using yeast two-hybrid assay and bimolecular fluorescence complementation assay, we determined that CsTTG1 directly interacts with Mict. Collectively, our results indicate that CsTTG1 is an important component of the molecular network that regulates fruit bloom trichome and wart formation in cucumber.

Silencing of the gibberellin receptor homolog, CsGID1a, affects locule formation in cucumber (Cucumis sativus) fruit.

Gibberellins are phytohormones with many roles, including the regulation of fruit development. However, little is known about the relationship between GA perception and fleshy fruit ontogeny, and particularly locule formation. We characterized the expression of cucumber (Cucumis sativus) GA receptor gene (CsGID1a) using quantitative real-time PCR, in situ hybridization and a promoter::ß-glucuronidase (GUS) assay. CsGID1a-RNAi cucumber fruits were observed by dissecting microscope, scanning electron microscopy and transmission electron microscopy. Finally, genome-wide gene expression in young fruits from a control and the RNAi line was compared using a digital gene expression (DGE) analysis approach. The expression pattern of CsGID1a was found to be closely correlated with fruit locule formation, and silencing CsGID1a in cucumber resulted in fruits with abnormal carpels and locules. Overexpression of CsGID1a in the Arabidopsis thaliana double mutant (gid1a gid1c) resulted in 'cucumber locule-like' fruits. The DGE analysis suggested that expression of genes related to auxin synthesis and transport, as well as the cell cycle, was altered in CsGID1a-RNAi fruits, a result that was supported by comparing the auxin content and cellular structures of the control and transgenic fruits. This study demonstrates a previously uncharacterized GA signaling pathway that is essential for cucumber fruit locule formation.