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SlARF10 plays an important role in the chlorophyll accumulation and photosynthesis of tomato plants, and regulation of its expression affects the starch, fructose, and sucrose content of fruit., The photosynthesis of green tomatoes contributes to fruit growth and carbon economy. The tomato auxin response factor 10 (SlARF10) belongs to the ARF family and is located in nucleus. In this study, we found that SlARF10 was highly expressed in green fruit. Overexpression of SlARF10 in fruit produced a dark-green phenotype whilst knock-down by RNAi produced a light-green phenotype. Autofluorescence and chlorophyll content analyses confirmed the phenotypes, which indicated that SlARF10 plays an important role in chlorophyll accumulation. Overexpression of SlARF10 positively affected photosynthesis in both leaves and fruit. Furthermore, SlARF10-overexpression lines displayed improved accumulation of starch, fructose, and sucrose in fruit, whilst SlARF10-RNAi lines showed decreased accumulation of starch and sucrose. Regulation of SlARF10 expression altered the expression of AGPase starch biosynthesis genes. SlARF10 positively regulated the expression of SlGLK1, POR, CBP1, and CBP2, which are related to chlorophyll metabolism and regulation. Electrophoretic mobility shift assays confirmed that SlARF10 directly targets to the SlGLK1 promoter. Our results thus indicate that SlARF10 is involved in chlorophyll accumulation by transcriptional activation of SlGLK1 expression in tomato fruit, and provide insights into the link between auxin signaling, chloroplast activity, and sugar metabolism during tomato fruit development.

Auxin response factors (ARFs) are involved in auxin-mediated transcriptional regulation in plants. In this study, we performed functional characterization of SlARF6A in tomato. SlARF6A is located in the nucleus and exhibits transcriptional activator activity. Overexpression of SlARF6A increased chlorophyll contents in the fruits and leaves of tomato plants, whereas downregulation of SlARF6A decreased chlorophyll contents compared with those of wild-type (WT) plants. Analysis of chloroplasts using transmission electron microscopy indicated increased sizes of chloroplasts in SlARF6A-overexpressing plants and decreased numbers of chloroplasts in SlARF6A-downregulated plants. Overexpression of SlARF6A increased the photosynthesis rate and accumulation of starch and soluble sugars, whereas knockdown of SlARF6A resulted in opposite phenotypes in tomato leaves and fruits. RNA-sequence analysis showed that regulation of SlARF6A expression altered the expression of genes involved in chlorophyll metabolism, photosynthesis and sugar metabolism. SlARF6A directly bound to the promoters of SlGLK1, CAB, and RbcS genes and positively regulated the expression of these genes. Overexpression of SlARF6A also inhibited fruit ripening and ethylene production, whereas downregulation of SlARF6A increased fruit ripening and ethylene production. SlARF6A directly bound to the SAMS1 promoter and negatively regulated SAMS1 expression. Taken together, these results expand our understanding of ARFs with regard to photosynthesis, sugar accumulation and fruit development and provide a potential target for genetic engineering to improve fruit nutrition in horticulture crops.

Tomato green fruits photosynthesis contributes to fruit growth and carbon economy. Tomato auxin response factor 10 (SlARF10) is one of the members of ARF family. Our results showed that SlARF10 locates in the nucleus and has no transcriptional activity. SlARF10 was expressed in various tomato tissues, but highly expressed in green fruit. Up-regulation of SlARF10 produced dark green phenotype of fruits, whereas down-regulation of SlARF10 had light green phenotype. Autofluorescence and chlorophyll content analysis confirmed the phenotypes, which indicated that SlARF10 plays an important role in chlorophyll accumulation in tomato fruits. Up-regulation of SlARF10 increased the photochemical potential in tomato leaves and fruits. Furthermore, the SlARF10 up-regulating lines displayed improved accumulation of starch in fruits, whereas SlARF10 suppressed lines had inhibited starch accumulation. Up-regulation of SlARF10 increased the expression of AGPases, the starch biosynthesis genes. SlARF10 up-regulating lines had increased accumulation of SlGLK1 and SlGLK2 transcripts in fruits. The promoter sequence of SlGLK1 gene had two conserved ARF binding sites. SlARF10 may regulate the expression of SlGLK1, thus controlling chlorophyll accumulation, photosynthesis rates and sugars synthesis in fruits. Our study provided more insight on the link between auxin signaling, chloroplastic activity and sugar metabolism during the development of tomato fruits.AbbreviationsARFsAuxin Response FactorsRNAiRNA interferenceGLKGOLDEN2-LIKEDET1/hp2The DE-ETIOLATED 1DDB1UV-DAMAGED DNA-BINDING PROTEIN 1KNOXsClass I KNOTTED1-LIKE HOMEOBOXGC-MSGas Chromatography-Mass SpectrometryqRT-PCRQuantitative real time PCRTFsTranscription factorsWTWild-typeMRMiddle regionDB domainDNA binding domainCTDC-terminal interaction domainADTranscriptional activatorsRDTranscriptional repressorsB3N-terminal DNA-binding domainHighlightSlARF10 played an important role in the chlorophyll accumulation and photosynthesis in tomato fruits. SlARF10 was involved in starch accumulation by controlling the expression of starch synthesis related enzyme genes. SlARF10 may regulate the expression of SlGLK1, thus controlling chlorophyll accumulation, photosynthesis rates and sugars synthesis in tomato fruits.

Background Hepatocellular carcinoma (HCC) has very high prevalence and associated-mortality. However, targeted therapies that are currently used in clinical practice for HCC have certain limitations, in part because of the lack of reliable and clinically applicable biomarkers that can be used for diagnosis and prognosis assessments and for the surveillance of treatment effectiveness. Methods Meta-analysis was used to analyze the integrated microarray data for global identification of a set of robust biomarkers for HCC. Quantitative RT-PCR (qRT-PCR) was performed to validate the expression levels of selected genes. Gene expression was inhibited by siRNA. CellTiter 96® AQueous One Solution Cell Proliferation assays were used to determine cell proliferation, and Transwell assays were used to determine cell migration and invasion potential. Results Meta-analysis of the expression data provided a gene expression signature from a total of 1525 patients with HCC, showing 1529 up-regulated genes and 478 down-regulated genes in cancer samples. The expression levels of genes having strong clinical significance were validated by qRT-PCR using primary HCC tissues and the paired adjacent noncancerous liver tissues. Up-regulation of VPS45, WIPI1, TTC1, IGBP1 and KLHL21 genes and down-regulation of FCGRT gene were confirmed in clinical HCC samples. KLHL21 was the most promising gene for potential use as a bioclinical marker in this analysis. Abrogating expression of it significantly inhibited cell proliferation, migration and invasion. Conclusions Our study suggests that KLHL21 is a potential target for therapeutic intervention. Our findings also provide novel candidate genes on a genome-wide scale, which may have significant impact on the design and execution of effective therapy of HCC patients. Electronic supplementary material The online version of this article (doi:10.1186/s12885-016-2851-7) contains supplementary material, which is available to authorized users.

The microarray gene expression datasets used in this study. (DOC 36 kb)

The literature confirmation for the identified genes from our bioinformatics analysis. (DOCX 47 kb)