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Introduction: Postharvest textural changes in fruit are mainly divided into softening and lignification. Loquat fruit could have severe lignification with increased firmness during postharvest storage. Pectin is mainly associated with the postharvest softening of fruit, but some studies also found that pectin could be involved in strengthening the mechanical properties of the plant. Objectives: This study focused on characterizing the dynamics of pectin and its complexation in the cell wall of lignified loquat fruit during postharvest storage, and how these changes could influence fruit firmness. Methods: The homogalacturonan (HG) pectin in the cell wall of loquat fruit was identified using monoclonal antibodies. An oligogalacturonide (OG) probe was used to label the egg-box structure formed by Ca2+ cross-linking with low-methylesterified HG. An exogenous injection was used to verify the role of egg-box structures in the firmness increase in loquat fruit. Results: The JIM5 antibody revealed that low-methylesterified HG accumulated in the tricellular junctions and middle lamella of loquat fruit that had severe lignification symptoms. The pectin methylesterase (PME) activity increased during the early stages of storage at 0 °C, and the calcium-pectate content and flesh firmness constantly increased during storage. The OG probe demonstrated the accumulation of egg-box structures at the cellular level. The exogenous injection of PME and Ca2+ into the loquat flesh led to an increase in firmness with more low-methylesterified HG and egg-box structure signals. Conclusion: PME-mediated demethylesterification generated large amounts of low-methylesterified HG in the cell wall. This low-methylesterified HG further cross-linked with Ca2+ to form egg-box structures. The pectin-involved complexations then contributed to the increased firmness in loquat fruit. Overall, besides being involved in fruit softening, pectin could also be involved in strengthening the mechanical properties of postharvest fruit. This study provides new ideas for obtaining a better texture of postharvest loquat fruits based on pectin regulation.

Sugars are the primary products of photosynthesis and play an important role in plant growth and development. They contribute to sweetness and flavor of fleshy fruits and are pivotal to fruit quality, and their translocation and allocation are mainly dependent on sugar transporters. Genome-wide characterization of Satsuma mandarin identified eighteen SWEET family members that encode transporters which facilitate diffusion of sugar across cell membranes. Analysis of the expression profiles in tissues of mandarin fruit at different developmental stages showed that CitSWEET11d transcripts were significantly correlated with sucrose accumulation. Further studies indicated that overexpression of CitSWEET11d in citrus callus and tomato fruit showed a higher sucrose level compared to wild-type, suggesting that CitSWEET11d could enhance sucrose accumulation. In addition, we identified an ERF transcription factor CitERF16 by yeast one-hybrid screening assay which could directly bind to the DRE cis-element on the promoter of CitSWEET11d. Overexpression of CitERF16 in citrus callus significantly induced CitSWEET11d expression and elevated sucrose content, suggesting that CitERF16 acts as a positive regulator to promote sucrose accumulation via trans-activation of CitSWEET11d expression.

Abstract Angiogenesis is essential for vascular development. The roles of regulatory long noncoding RNAs (lncRNAs) in mediating angiogenesis remain under‐explored. Human embryonic stem cell‐derived mesenchymal stem cells (hES‐MSCs) are shown to exert more potent cardioprotective effects against cardiac ischemia than human bone marrow‐derived MSCs (hBM‐MSCs), associated with enhanced neovascularization. The purpose of this study is to search for angiogenic lncRNAs enriched in hES‐MSCs, and investigate their roles and mechanisms. AC103746.1 is one of the most highly expressed intergenic lncRNAs detected in hES‐MSCs versus hBM‐MSCs, and named as SCDAL (stem cell‐derived angiogenic lncRNA). SCDAL knockdown significantly reduce the angiogenic potential and reparative effects of hES‐MSCs in the infarcted hearts, while overexpression of SCDAL in either hES‐MSCs or hBM‐MSCs exhibits augmented angiogenesis and cardiac function recovery. Mechanistically, SCDAL induces growth differentiation factor 6 (GDF6) expression via direct interaction with SNF5 at GDF6 promoter. Secreted GDF6 promotes endothelial angiogenesis via non‐canonical vascular endothelial growth factor receptor 2 activation. Furthermore, SCDAL‐GDF6 is expressed in human endothelial cells, and directly enhances endothelial angiogenesis in vitro and in vivo. Thus, these findings uncover a previously unknown lncRNA‐dependent regulatory circuit for angiogenesis. Targeted intervention of the SCDAL‐GDF6 pathway has potential as a therapy for ischemic heart diseases.

Correlation analysis is a routine method of biological data analysis. In the process of RNA-Seq analysis, differentially expressed genes could be identified by calculating the correlation coefficients in the comparison of gene expression vs. phenotype or gene expression vs. gene expression. However, due to the complicated genetic backgrounds of perennial fruit, the correlation coefficients between phenotypes and genes are usually not high in fruit quality studies. In this study, a cluster-based correlation analysis method (C-CorA) is presented for fruit RNA-Seq analysis. C-CorA is composed of two main parts: the clustering analysis and the correlation analysis. The algorithm is described and then integrated into the MATLAB code and the C# WPF project. The C-CorA method was applied to RNA-Seq datasets of loquat (Eriobotrya japonica) fruit stored or ripened under different conditions. Low temperature conditioning or heat treatment of loquat fruit can alleviate the extent of lignification that occurs because of postharvest storage under low temperatures (0 °C). The C-CorA method generated correlation coefficients and identified many candidate genes correlated with lignification, including EjCAD3 and EjCAD4 and transcription factors such as MYB (UN00328). C-CorA is an effective new method for the correlation analysis of various types of data with different dimensions and can be applied to RNA-Seq data for candidate gene detection in fruit quality studies.

Cell-type transcriptome profiling greatly elucidate organismal development. Here, the authors report a spatiotemporally resolved comprehensive transcriptome analysis of tomato fruit ontogeny and suggest a new model of fruit maturation which initiates in internal tissues then radiates outwards.

‘Jimba’ is a white chrysanthemum cultivar, which occasionally and spontaneously produces red flower petals under natural cultivation due to cyanidin-based anthocyanin accumulation. To investigate the underlying mechanism of this process, a comparative transcriptome was analyzed between white and turning red ‘Jimba’. The structural and regulatory genes of anthocyanin pathway were significantly up-regulated in turning red ‘Jimba’. Among them, two alternative splicings, CmbHLH2 and CmbHLH2.1, showed the most significantly up-regulated in turning red tissue. Transiently over-expressed 35S::CmMYB6-CmbHLH2 strongly induced anthocyanin accumulation in ‘Jimba’ flower petals, while moderate amount of anthocyanin was detected when over-expressed 35S::CmMYB6-CmbHLH2.1. Both CmbHLH2 and CmbHLH2.1 could interact with CmMYB6 to activate CmDFR promoter according to Yeast two-hybrid and dual-luciferase assay. Moreover, CmMYB6-CmbHLH2 but not CmMYB6-CmbHLH2.1 could activate the CmbHLH2 promoter to provide positive feedback loop regulation. Taken together, it suggested that both CmbHLH2 and CmbHLH2.1 involved in regulation flower color alteration in turning red ‘Jimba’, and CmbHLH2 played a predominant role in this process.

Volatile compounds principally contribute to flavor of strawberry (Fragaria × ananassa) fruit. Besides to genetics, cultivation conditions play an important role in fruit volatile formation. Compared to soil culture as control, effects of substrate culture on volatile compounds of two strawberry cultivars (‘Amaou’ and ‘Yuexin’) were investigated. GC-MS analysis revealed significant difference in volatile contents of ‘Amaou’ strawberry caused by substrate culture. No significant effect was observed for cultivar ‘Yuexin’. For ‘Amaou’ strawberry from soil culture produced higher volatile contents compared with substrate culture. This difference is contributed by high contents of esters, lactones, ketones, aldehydes, terpenes, hydrocarbons, acids, furans and phenols in ‘Amaou’ strawberry fruit from soil culture. Furanones, beta-linalool, trans-Nerolidol and esters are major contributor to strawberry aroma, whose contents are higher in soil culture planted fruit when compared to substrate culture. Moreover, strawberry fruit from soil culture had higher transcripts related to volatile biosynthesis were observed, including FaQR, FaOMT, FaNES1, FaSAAT and FaAAT2.

A major cause of transplanted organ failure is graft arteriosclerosis. Qiuet al. show that a key protease of post-translational SUMO modification, SENP1, is crucial for graft arteriosclerosis by regulating the activity of GATA2 transcription factor in the endothelium, and promoting endothelial inflammation and alloimmunity.