Physiological characterization of leaf and internode after bud break in Japanese indigenous Koshu grape by comparative RNA sequencing analysis

MOS4-associated complex contributes to proper splicing and suppression of ER stress under long-term heat stress in Arabidopsis

Plants are often exposed not only to short-term (S-) but also to long-term (L-)heat stress over several consecutive days. A few Arabidopsis mutants defective in L-heat tolerance have been identified, but the molecular mechanisms are less understood for this tolerance than for S-heat stress tolerance. To elucidate the mechanisms of the former, we used a forward genetic screen for sensitive to long-term heat (sloh) mutants and isolated sloh3 and sloh63. The mutants were hypersensitive to L- but not to S-heat stress, and sloh63 was also hypersensitive to salt stress. We identified the causal genes, SLOH3 and SLOH63, both of which encoded splicing-related components of the MOS4-associated complex (MAC). This complex is widely conserved in eukaryotes and has been suggested to interact with spliceosomes. Both genes were induced by L-heat stress in a time-dependent manner, and some abnormal splicing events were observed in both mutants under L-heat stress. In addition, endoplasmic reticulum (ER) stress and subsequent unfolded protein response occurred in both mutants under L-heat stress and were especially prominent in sloh63, suggesting that enhanced ER stress is due to the salt hypersensitivity of sloh63. Splicing inhibitor pladienolide B led to concentration-dependent disturbance of splicing, decreased L-heat tolerance, and enhanced ER stress. These findings suggest that maintenance of precise mRNA splicing under L-heat stress by the MAC is important for L-heat tolerance and suppressing ER stress in Arabidopsis.

Grape cytochrome P450 CYP90D1 regulates brassinosteroid biosynthesis and increases vegetative growth

Vine vigor or vegetative growth is an important factor related to berry quality and vinicultural training management, but brassinosteroid (BR)-induced molecular mechanisms underlying vine growth remain unclear. In this study, the hypothesis that the Vitis vinifera CYP90D1 gene VvCYP90D1, one of the genes for BR biosynthesis, plays a critical role in shoot elongation was tested. RNA sequencing analysis of shoots collected from the vigorous cultivar Koshu (KO) and the reference cultivar Pinot Noir (PN) 7 days after bud break showed higher expression levels of various genes in the BR biosynthesis pathway in KO than in PN. The VvCYP90D1 expression level in KO was highest in meristems, followed by internodes and leaves. Cluster analysis of amino acid sequences including those in other plant species showed that the isolated gene belonged to the CYP90D1 group. The vegetative growth and the endogenous BR (brassinolide; BL) content were significantly higher in VvCYP90D1-overexpressing Arabidopsis than in wild type. VvCYP90D1-overexpressing Arabidopsis treated with brassinazole (Brz), a BR biosynthesis inhibitor, showed recovery of vegetative growth. These results indicate that VvCYP90D1 in grapevine has a vegetative growth promoting effect via BR biosynthesis. Our findings on the mechanism of BR-induced grape shoot growth will contribute to the development of new shoot control techniques for grapevine.

Genomic Characterization of the Japanese Indigenous Wine Grape Vitis sp. cv. Koshu

Vitis sp. cv. Koshu is indigenous to Japan and used as a table and processing grape. It also constitutes an important grape cultivar in Japanese white wine making and is phylogenetically distinct from European grapes. To understand its genomic information, we compared its small and structural variations with those of the table grape cultivar "Thompson seedless" and European wine grape cultivar "Tannat" via a short-read-based resequencing approach. The Koshu genome exhibited high heterozygosity compared to these cultivars, with this characteristic being particularly prominent on chromosome 7. Furthermore, Koshu structural variation encompassed the most and largest extent of duplications and the fewest and smallest extent of deletions with regard to copy number variation and the fewest absence variations among the compared grape cultivars. Plant disease resistance related to cell death associated with hypersensitive response and environmental stress response, such as water deprivation, oxidative stress, and cell wall organization, was inferred through enrichment analysis of small and structural variations. Variant accumulation levels in Koshu indicated that phenylpropanoid, flavonoid, glutathione, and α-linolenic acid pathways were related to polyphenol and flavor components. Together, this Koshu genomic information provides a foundation for improving the quality of Koshu wine and may facilitate the use of Koshu as a genetic resource.

Transcriptomic and metabolomic analyses of Lycium ruthenicum and Lycium barbarum fruits during ripening

Red wolfberry (or goji berry, Lycium barbarum; LB) is an important agricultural product with a high content of pharmacologically important secondary metabolites such as phenylpropanoids. A close relative, black wolfberry (L. ruthenicum; LR), endemic to the salinized deserts of northwestern China, is used only locally. The two fruits exhibit many morphological and phytochemical differences, but genetic mechanisms underlying them remain poorly explored. In order to identify the genes of interest for further studies, we studied transcriptomic (Illumina HiSeq) and metabolomic (LC-MS) profiles of the two fruits during five developmental stages (young to ripe). As expected, we identified much higher numbers of significantly differentially regulated genes (DEGs) than metabolites. The highest numbers were identified in pairwise comparisons including the first stage for both species, but total numbers were consistently somewhat lower for the LR. The number of differentially regulated metabolites in pairwise comparisons of developmental stages varied from 66 (stages 3 vs 4) to 133 (stages 2 vs 5) in both species. We identified a number of genes (e.g. AAT1, metE, pip) and metabolites (e.g. rutin, raffinose, galactinol, trehalose, citrulline and DL-arginine) that may be of interest to future functional studies of stress adaptation in plants. As LB is also highly suitable for combating soil desertification and alleviating soil salinity/alkalinity/pollution, its potential for human use may be much wider than its current, highly localized, relevance.