Fruit quality is an important trait in strawberry and is determined by many factors. The soluble solid content in strawberry fruits is positively related to the phosphorus content. MicroRNA399 (miR399) is involved in the regulation of phosphate (Pi) homeostasis. However, the effect of miR399 on strawberry quality remains unknown. In this study, miR399a-overexpressing transgenic woodland strawberries (Fragaria vesca) were obtained via an Agrobacterium-mediated transformation. The phosphorus (P) content was 1.1-fold to 2.1-fold higher in the leaves and fruits of the miR399a-overexpressing plants than in the wild type (WT). However, the P content in the miR399a-overexpressing plants was decreased by 25% to 45% in the roots. The primary root length of the transgenic lines in both the high-Pi and low-Pi media was shorter than that of the WT. Interestingly, the transgenic lines in pots under Pi-sufficient conditions grew better than the WT, and the fruit quality, including the contents of fructose and glucose and soluble solid, was significantly higher in the transgenic lines than in the WT. The overexpression of miR399a in strawberry can be used to improve the parameters involved in fruit quality and provides information regarding breeding nutrient-improved strawberry.

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by base pairing to mRNA target sequences, and play crucial roles in plant development and stress responses. The knowledge on post-transcriptional regulation by miRNAs in strawberry is rather limited so far. In order to understand the role of miRNA in the molecular control during strawberry fruit development, small RNA libraries were constructed from fruits at the turning stage of strawberry cultivar 'Sachinoka' and its white-flesh mutant by using the Solexa platform. One hundred and twenty conserved miRNAs belonging to 27 miRNA families and 33 putative novel strawberry miRNAs were identified in both libraries. Their target genes were predicted using the Fragaria vesca genome. Nine of all miRNAs showed significant expression differences between two types of samples. Four miRNAs were up-regulated and five were down-regulated in white-flesh mutant. The sequencing results were partially validated by quantitative RT-PCR. Among them, the expression of miR399a shows the biggest change between the two samples. The prediction of its target gene showed that miR399 may play an important role in phosphate homeostasis of strawberry fruits. Furthermore, we deduce that the expression of miR399 has negative correlation with the content of sugars.

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The P2X₇R (P2X₇ receptor) is an ATP-gated cation channel expressed in normal cells that participates in both cell proliferation and apoptosis. Here, we have confirmed P2X₇R expression on murine P388D1 lymphoid neoplasm cells. In addition, ATP-stimulated P2X₇R expression was found to trigger increased intracellular calcium flux. Furthermore, silencing with short hairpin RNA and blocking with P2X₇R antibody significantly reduced the metastasis of P388D1 cells to lymph nodes. These results indicate that inhibition of the expression and function of P2X₇R attenuates the metastatic ability of murine lymphoid neoplasm cell line P388D1, which represents a new potential target for anti-metastatic therapy.

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