Anthocyanins are water-soluble pigments in plants. They confer both economical and healthy profits for humans. To gain a deeper insight into the regulation of anthocyanins biosynthesis in octoploid strawberry (Fragaria × ananassa; Fa), a widely-consumed economically important fruit, we performed comparative transcriptomic analysis of red- and white-fleshed strawberry cultivars in two ripening stages. In total, 365,455 non-redundant transcripts were assembled from the RNA sequencing (RNAseq) data. Of this collection, 377 were annotated as putative anthocyanins related transcripts. Differential expression analysis revealed that 57 anthocyanins biosynthesis transcripts were down-regulated, and 89 transcription factors (TFs) were either down- or up- regulated under anthocyanins deficiency. Additionally, amongst the 50,601 putative long non-coding RNAs (lncRNAs) identified here, 68 lncRNAs were differentially expressed and co-expressed with differentially expressed anthocyanins related mRNAs, 2,070 co-expressing lncRNAs-mRNAs pairs were generated. Expression profiles analysis revealed that it was the limited expression of FaF3'H that blocked the cyanidin 3-glucoside accumulation in the two investigated strawberry cultivars. This was further supported by a transient-overexpression experiment with FaMYB10. The down-regulated lncRNAs might participate in anthocyanins regulation by acting as targets for micro RNAs (miRNAs). The level of competitive intensity in miRNA and lncRNA for the same mRNAs target was probably lower in the white-fleshed strawberries, which can release the repression effect of the mRNAs in red-fleshed strawberry as a result. This study for the first time presents lncRNAs related to anthocyanins in strawberries, provides new insights into anthocyanins regulatory network, and also lays the foundation for identifying new anthocyanins regulators in strawberry.

The carotenoid isomerase gene (BoaCRTISO) of Chinese kale was targeted and edited using the CRISPR/Cas9 system in the present study. The results showed a high mutation rate (81.25%), and 13 crtiso mutants were obtained. Only two types of mutations, insertions and replacements, were found. Both the total and individual carotenoid and chlorophyll concentrations of the biallelic and homozygous mutants were reduced, and the total levels declined by 11.89–36.33%. The color of the biallelic and homozygous mutants changed from green to yellow, likely reflecting a reduction in the color-masking effect of chlorophyll on carotenoids. The expression levels of most carotenoid and chlorophyll biosynthesis-related genes, including CRTISO, were notably lower in the mutants than in the WT plants. In addition, the functional differences between members of this gene family were discussed. In summary, these findings indicate that CRISPR/Cas9 is a promising technique for the quality improvement of Chinese kale and other Brassica vegetables.

No abstract

Rosaceae comprises numerous types of economically important fruits, ornamentals, and timber. The lack of plastome characteristics has blocked our understanding of the evolution of plastome and plastid genes of Rosaceae crops. Using comparative genomics and phylogenomics, we analyzed 121 Rosaceae plastomes of 54 taxa from 13 genera, predominantly including Cerasus (true cherry) and its relatives. To our knowledge, we generated the first comprehensive map of genomic variation across Rosaceae plastomes. Contraction/expansion of inverted repeat regions and sequence losses of the two single-copy regions underlie large genomic variations in size among Rosaceae plastomes. Plastid protein-coding genes were characterized with a high proportion (over 50%) of synonymous variants and insertion-deletions with multiple triplets. Five photosynthesis-related genes were specially selected in perennial woody trees. Comparative genomic analyses implied divergent evolutionary patterns between pomaceous and drupaceous trees. Across all examined plastomes, unique and divergent evolution was detected in Cerasus plastomes. Phylogenomic analyses and molecular dating highlighted the relatively distant phylogenetic relationship between Cerasus and relatives (Microcerasus, Amygdalus, Prunus, and Armeniaca), which strongly supported treating the monophyletic true cherry group as a separate genus excluding dwarf cherry. High genetic differentiation and distinct phylogenetic relationships implied independent origins and domestication between fruiting cherries, particularly between Prunus pseudocerasus (Cerasus pseudocerasus) and P. avium (C. avium). Well-resolved maternal phylogeny suggested that cultivated P. pseudocerasus originated from Longmenshan Fault zone, the eastern edge of Himalaya-Hengduan Mountains, where it was subjected to frequent genomic introgression between its presumed wild ancestors and relatives.

Strawberry is often subjected to cold stress in temperate regions when insulation measures are not strictly applied in protected cultivation. Cold stress adversely influences plant growth and development by triggering a massive change to the transcriptome. To provide the potential strategies in improving strawberry cold tolerance and give a glimpse into the understanding of the complex cold signaling pathways in plants, this study identified attractive candidate genes and revealed diverse regulatory networks that responded to cold stress in strawberry (Fragaria×ananassa) by a transcriptomic analysis. Totally, there were 2397 differentially expressed genes (DEGs) under cold stress treatment (T1) vs. normal treatment (CK). Of these, 1180 DEGs were upregulated, while 1217 DEGs were downregulated. Functional enrichment analysis showed that DEGs were significantly (adjusted P value < 0.05) overrepresented in six pathways including plant hormone signal transduction, flavonoid biosynthesis, mitogen-activated protein kinase (MAPK) signaling, starch and sucrose metabolism, circadian rhythm, and alpha-linolenic acid metabolism. The cold signaling initiated expression of downstream cold-responsive (COR) genes with cis-acting element ABRE or CRT/DRE in the ABA-independent or ABA-dependent pathway to impel plant defense against the stress. Strikingly, GIGANTEA (gene id 101308922), two-component response regulator-like PRR95 (gene id 101295449), and ethylene-responsive transcription factor ERF105-like (gene id 101295082) were dramatically induced under low-temperature treatment, indicating that they played an important role in response to cold stress in strawberry.

To investigate the molecular mechanism underlying fruit development and color change, comparative transcriptome analysis was employed to generate transcriptome profiles of two typical wild varieties of Fragaria pentaphylla at three fruit developmental stages (green fruit stage, turning stage, and ripe fruit stage). We identified 25,699 long noncoding RNAs (lncRNAs) derived from 25,107 loci in the F. pentaphylla fruit transcriptome, which showed distinct stage- and genotype-specific expression patterns. Time course analysis detected a large number of differentially expressed protein-coding genes and lncRNAs associated with fruit development and ripening in both of the F. pentaphylla varieties. The target genes downregulated in the late stages were enriched in terms of photosynthesis and cell wall organization or biogenesis, suggesting that lncRNAs may act as negative regulators to suppress photosynthesis and cell wall organization or biogenesis during fruit development and ripening of F. pentaphylla . Pairwise comparisons of two varieties at three developmental stages identified 365 differentially expressed lncRNAs in total. Functional annotation of target genes suggested that lncRNAs in F. pentaphylla may play roles in fruit color formation by regulating the expression of structural genes or regulatory factors. Construction of the regulatory network further revealed that the low expression of Fra a and CHS may be the main cause of colorless fruit in F. pentaphylla .

The plant sucrose nonfermenting 1 (SNF1)-related protein kinases (SnRKs) are key regulators in the interconnection of various signaling pathways. However, little is known about the SnRK family in strawberries. In this study, a total of 26 FvSnRKs including one FvSnRK1, nine FvSnRK2s and 16 FvSnRK3s were identified from the strawberry genome database. They were respectively designated as FvSnRK1.1, FvSnRK2.1 to FvSnRK2.9 and FvSnRK3.1 to FvSnRK3.16, according to the conserved domain of each subfamily and multiple sequence alignment with Arabidopsis. FvSnRK family members were unevenly distributed in seven chromosomes. The number of exons or introns varied among FvSnRK1s, FvSnRK2s and FvSnRK3s, but highly conserved in the same subfamily. The FvSnRK1.1 had 10 exons. Most of FvSnRK2s had nine exons or eight introns, except FvSnRK2.4, FvSnRK2.8 and FvSnRK2.9. FvSnRK3 genes were divided into intron-free and intron-harboring members, and the number of introns in intron-harboring group ranged from 11 to 15. Moreover, the phylogenetic analysis showed SnRK1, SnRK2 and SnRK3 subfamilies respectively clustered together in spite of the different species of strawberry and Arabidopsis, indicating the genes were established prior to the divergence of the corresponding taxonomic lineages. Meanwhile, conserved motif analysis showed that FvSnRK sequences that belonged to the same subgroup contained their own specific motifs. Cis-element in promoter and expression pattern analyses of FvSnRK1.1 suggested that FvSnRK1.1 was involved in cold responsiveness, light responsiveness and fruit ripening. Taken together, this comprehensive analysis will facilitate further studies of the FvSnRK family and provide a basis for the understanding of their function in strawberry.

Strawberry is a typical nonclimacteric fruit, whose ripening mechanism needs to be further investigated. Sucrose has been recently proved as a signal molecule, participating in strawberry fruit ripening and related processes. While in the effects of sucrose application timing and concentration on ripening, fruit qualities remain unclear, as well as the transcriptome-wide details about the effects of sucrose on the gene expression involved in ripening-related processes. In this study, strawberry fruits at the degreening (DG), white (W), and initial-red (IR) stages were treated with different concentration of sucrose. The results showed that anthocyanin was increased while total polyphenol concentration (TPC) and total flavonoid concentration (TFC) were decreased during fruit development after sucrose treatment. Interestingly, It was showed that 100 mM sucrose application at the DG stage had the most obvious effects on fruit ripening; it made all the fruits turn into full-red (FR) around 4 days (d) earlier than the control, while it did not affect fruit quality traits and most bioactive compounds in the FR fruits. Subsequently, RNA sequencing (RNAseq) of the fruits collected at 8 days after 100 mM sucrose treatment was carried out. It was suggested that 993 genes were differentially expressed comparing with the control. Transcriptome-based expression analysis revealed that sucrose induced the expression of genes involved in the AsA and anthocyanin biosynthesis, while largely suppressed the expression of genes in TCA. The results obtained in this study provided more expression profiles of ripening-related genes under the treatment of sucrose, which will contribute to a better understanding for the mechanism underlying sucrose-induced fruit ripening.