Sucrose synthase (SS) is widely considered as the key enzyme involved in the plant sugar metabolism that is critical to plant growth and development, especially quality of the fruit. The members of SS gene family have been identified and characterized in multiple plant genomes. However, detailed information about this gene family is lacking in grapevine (Vitis vinifera L.). In this study, we performed a systematic analysis of the grape (V. vinifera) genome and reported that there are five SS genes (VvSS1–5) in the grape genome. Comparison of the structures of grape SS genes showed high structural conservation of grape SS genes, resulting from the selection pressures during the evolutionary process. The segmental duplication of grape SS genes contributed to this gene family expansion. The syntenic analyses between grape and soybean (Glycine max) demonstrated that these genes located in corresponding syntenic blocks arose before the divergence of grape and soybean. Phylogenetic analysis revealed distinct evolutionary paths for the grape SS genes. VvSS1/VvSS5, VvSS2/VvSS3 and VvSS4 originated from three ancient SS genes, which were generated by duplication events before the split of monocots and eudicots. Bioinformatics analysis of publicly available microarray data, which was validated by quantitative real-time reverse transcription PCR (qRT-PCR), revealed distinct temporal and spatial expression patterns of VvSS genes in various tissues, organs and developmental stages, as well as in response to biotic and abiotic stresses. Taken together, our results will be beneficial for further investigations into the functions of SS gene in the processes of grape resistance to environmental stresses.

Grapevine, Vitis vinifera, is an important economic fruit crop that is highly sensitive to gibberellin (GA), and the exogenous application of GA can efficiently induce grapevine parthenocarpy. However, the molecular mechanisms underlying this process remain elusive. In this study, morphological changes during flower development in response to GA treatments were examined in the ‘Zuijinxiang’ cultivar. To obtain insights into the roles of miRNA159s in GA-induced grapevine parthenocarpy, VvmiR159a, VvmiR159b, VvmiR159c, and their target gene VvGAMYB were isolated, sequenced and characterized. Spatial-temporal expression analyses showed that VvmiR159c exhibited the highest expression levels at 4 d before flowering, followed by a gradual decrease, while VvGAMYB displayed an opposite pattern of expression with the lowest expression at the corresponding stage in response to GA treatment. A cleavage interaction between VvmiR159s and VvGAMYB and variations of their cleavage roles were confirmed in grapevine floral development. In addition, the potential roles of VvmiR159s in GA signaling were investigated through DELLA-protein repressors, indicating that GA–DELLA (SLR1)–VvmiR159c–VvGAMYB is the key signaling regulatory module in grapevine. Our findings provide novel insights into the GA-responsive roles of VvmiR159s in modulating grapevine floral development, which have important implications for the molecular breeding of high-quality seedless grapevine berry.

The microRNA171 (miR171) family is widely distributed and highly conserved in a range of species and plays critical roles in regulating plant growth and development through repressing expression of SCARECROW‐LIKE ( SCL ) transcription factors. However, information on the evolutionary conservation and functional diversification of the miRNA171 family members remains scanty. We reconstructed the phylogenetic relationships among miR171 precursor and mature sequences so as to investigate the extent and degree of evolutionary conservation of miR171 in Arabidopsis thaliana (L.) Heynh. (ath), grape ( Vitis vinifera L.) (vvi), poplar ( Populus trichocarpa Torr. & A.Gray ex Hook.) (ptc), and rice ( Oryza sativa L.) (osa). Despite strong conservation of over 80%, some mature miR171 sequences, such as ptc‐miR171j ‐l , and ‐m and osa‐miR171g , ‐ h , and ‐ i , have undergone critical sequence variation, leading to functional diversification, since they target non ‐SCL gene transcript(s). Phylogenetic analyses revealed a combination of old ancestral relationships and recent lineage‐specific diversification in the miR171 family within the four model plants. The cis ‐regulatory motifs on the upstream promoter sequences of miR171 genes were highly divergent and shared some similar elements, indicating their possible contribution to the functional variation observed within the miR171 family. This study will buttress our understanding of the functional differentiation of miRNAs and the relationships of miRNA–target pairs based on the evolutionary history of miRNA genes.

Background: MicroRNAs (miRNAs), involving in various biological and metabolic processes, have been discovered and analyzed in quite a number of plants species, such as Arabidopsis, rice and other plants. However, there have been few reports about grapevine miRNAs in response to gibberelline (GA₃). Results: Solexa technology was used to sequence small RNA libraries constructed from grapevine berries treated with GA₃ and the control. A total of 122 known and 90 novel grapevine miRNAs (Vvi-miRNAs) were identified. Totally, 137 ones were found to be clearly responsive to GA₃, among which 58 were down-regulated, 51 were up-regulated, 21 could only be detected in the control, and seven were only detected in the treatment. Subsequently, we found that 28 of them were differentially regulated by GA₃, with 12 conserved and 16 novel Vvi-miRNAs, based on the analysis of qRT-PCR essays. There existed some consistency in expression levels of GA₃-responsive Vvi-miRNAs between high throughput sequencing and qRT-PCR essays. In addition, 117 target genes for 29 novel miRNAs were predicted. Conclusions: Deep sequencing of short RNAs from grapevine berries treated with GA3 and the control identified 137 GA₃-responsive miRNAs, among which 28 exhibited different expression profiles of response to GA₃ in the diverse developmental stages of grapevine berries. These identified Vvi-miRNAs might be involved in the grapevine berry development and response to environmental stresses.