Exogenous 24-Epibrassinolide Interacts with Light to Regulate Anthocyanin and Proanthocyanidin Biosynthesis in Cabernet Sauvignon (Vitis vinifera L.)

Brassinosteroid Promotes Grape Berry Quality-Focus on Physicochemical Qualities and Their Coordination with Enzymatic and Molecular Processes: A Review

Brassinosteroid (BR) is an important endogenous phytohormone that plays a significant role in fruit quality regulation. The regulation of BR biosynthesis and its physiological effects have been well-studied in various fruits. External quality (fruit longitudinal and transverse diameters, firmness, single berry weight, color) and internal quality (sugars, aroma, anthocyanin, stress-related metabolites) are important parameters that are modified during grape berry development and ripening. Grapevines are grown all over the world as a cash crop and utilized for fresh consumption, wine manufacture, and raisin production. In this paper, the biosynthesis and signaling transduction of BR in grapevine were summarized, as well as the recent developments in understanding the role of BR in regulating the external quality (fruit longitudinal and transverse diameters, firmness, single berry weight, and color) and internal quality (sugars, organic acids, aroma substances, anthocyanins, antioxidants) of grapes. Additionally, current advancements in exogenous BR strategies for improving grape berries quality were examined from the perspectives of enzymatic activity and transcriptional regulation. Furthermore, the interaction between BR and other phytohormones regulating the grape berry quality was also discussed, aiming to provide a reliable reference for better understanding the potential value of BR in the grape/wine industry.

The influences of fungal endophytes inoculation on the biochemical status of grape cells of different varieties in vitro

The metabolic patterns of grape cells can be specifically shaped by different strains of dual-cultured fungal endophytes. In this work, a solid co-culture system was furtherly proposed to illustrate the different impacts of endophytic fungi on the biochemical status of grape cells of different varieties. By measuring the metabolic impacts of contact fungal endophytes on grape cells of the varieties 'Rose honey' (RH) and 'Cabernet sauvignon' (CS), we observed that most of the fungal strains used had promoting effects on grape cellular biochemistry parameters. Compared with the control, inoculation with most of the fungal strains increased the superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL) activities as well as the total flavonoid (TF) and total phenolics (TPh) contents in both types of grape cells. Among the tested strains, RH34, RH49 and MDR36 had relatively stronger biochemical impacts on grape cells. More interestingly, in addition to the varietal specificity, a certain degree of fungal genus specificity was also observed during the metabolic interactions between fungal endophytes and grape cells, as fungal endophytes from the same genus tended to be clustered into the same group based on the affected biochemical traits. This work revealed the differential biochemical status effects of fungal endophytes on different varietal grape cells and raised the possibility of reshaping grape qualities by applying endophytes.

Improving berry quality and antioxidant ability in 'Ruidu Hongyu' grapevine through preharvest exogenous 2,4-epibrassinolide, jasmonic acid and their signaling inhibitors by regulating endogenous phytohormones

Grape berries contain a variety of metabolites, such as anthocyanins, sugars, fatty acids, and antioxidants. Endogenous phytohormones strongly influence these metabolites, which regulate berry quality improvement. In this study, we evaluated the effects of 2,4-epibrassinolide (EBR, brassinolide (BR)-like growth regulator), jasmonic acid (JA), and their signaling inhibitors brassinazole (Brz), and sodium diethyldithiocarbamate (DIECA) on berry quality and antioxidant ability. Overall, the pre-harvest application of 0.5 mg L^-1 EBR and 100 μmol L^-1 JA significantly influences the quality of the grape berry. Results showed that EBR was superior to other treatments at enhancing the content of different metabolites, including anthocyanins, fructose, glucose, and a variety of fatty acids, in grapes. EBR and JA also enhanced the synthesis of gibberellin₃ (GA₃), cytokinin (CTK), salicylic acid (SA), JA, methyl jasmonate (MeJA), BR, and abscisic acid (ABA), while inhibiting the synthesis of auxin (IAA). Most genes related to BR/JA and anthocyanins/sugars/fatty acids biosynthesis were up-regulated. The effects of Brz and DIECA on the grape berry quality were totally reversed throughout the study, as shown by EBR and JA. According to correlation analysis, EBR and JA have a beneficial positive interaction that promotes the formation of strong coherences in grape berries between ABA/IAA/ZT-fruit expansion, BR/JA/MeJA/GA₃/ZR-biochemical characteristics development, JA/MeJA/ABA/GA₃/SA/ZR-antioxidant capacity enhancement, and JA/MeJA/IAA/GA₃/ZT/ZR-fatty acids accumulation. In this regard, we concluded that preharvest exogenous 0.5 mg L^-1 EBR and 100 μmol L^-1 JA is a successful way to improve grape berry quality.

Anthocyanin Biosynthesis and a Regulatory Network of Different-Colored Wheat Grains Revealed by Multiomics Analysis

Colored wheat has always been a popular research area because of its high performance in the field and significant medical uses. Progress has been made mapping the genes of purple or blue grains; however, the reason why different grain colors form in wheat is not well understood. We created wheat lines with different grain colors (purple and blue) using the white grain cultivar Xiaoyan22 and located the candidate region related to the purple and blue grains in chromosome 2A, 2B, and 4D, 2A, respectively, by the bulked segregant RNA-seq. The transcriptomic and metabolomic analyses of the three grains at different developmental stages indicated that the upregulation of flavonoid 3'-hydroxylase/flavonoid 3',5'hydroxylase 2 and TaMYC1/TaMYC4 was important for the formation of purple/blue grains. The blue TaMYC4 had 16 nonsynonymous single nucleotide variants verified by Sanger sequencing and possessed a different splicing mode in the bHLH_MYC_N domain compared with the reference database. Targeted high-performance liquid chromatography-mass spectrometry/mass spectrometry analysis of anthocyanins found that the purple and blue grains contained more pelargonidin, cyanidin, and delphinidin, respectively. This study provides a comprehensive understanding of the different color formations of wheat grains and useful information about genetic improvements in wheat and other crops.

Emerging roles of brassinosteroids and light in anthocyanin biosynthesis and ripeness of climacteric and non-climacteric fruits

Anthocyanins are important pigments that contribute to fruit quality. The regulation of anthocyanin biosynthesis by several transcription factors via sophisticated regulatory networks has been studied in various plants. Brassinosteroids (BRs), a new class of plant hormone, are involved in regulating anthocyanin biosynthesis in fruits. Furthermore, light directly affects the synthesis and distribution of anthocyanins. Here, we summarize the recent progress toward understanding the impact of BR and light on anthocyanin biosynthesis in climacteric and non-climacteric fruits. We review the BR and light signaling pathways and highlight the important transcription factors that are associated with the synthesis of anthocyanins, such as BZR1 (brassinazole-resistant 1, BR signaling pathway), HY5 (elongated hypocotyl 5) and COP1 (constitutively photomorphogenic 1, light signal transduction pathway), which bind with the target genes involved in anthocyanin synthesis. In addition, we review the mechanism by which light signals interact with hormonal signals to regulate anthocyanin biosynthesis.

Comparative Metabolite and Gene Expression Analyses in Combination With Gene Characterization Revealed the Patterns of Flavonoid Accumulation During Cistus creticus subsp. creticus Fruit Development

Cistus creticus L. subsp. creticus (rockrose) is a shrub widespread in Greece and the Mediterranean basin and has been used in traditional medicine as herb tea for colds, for healing and digestive hitches, for the treatment of maladies, as perfumes, and for other purposes. Compounds from its flavonoid fraction have recently drawn attention due to antiviral action against influenza virus and HIV. Although several bioactive metabolites belonging to this group have been chemically characterized in the leaves, the genes involved in their biosynthesis in Cistus remain largely unknown. Flavonoid metabolism during C. creticus fruit development was studied by adopting comparative metabolomic and transcriptomic approaches. The present study highlights the fruit of C. creticus subsp. creticus as a rich source of flavonols, flavan-3-ols, and proanthocyanidins, all of which displayed a decreasing trend during fruit development. The majority of proanthocyanidins recorded in Cistus fruit are B-type procyanidins and prodelphinidins, while gallocatechin and catechin are the dominant flavan-3-ols. The expression patterns of biosynthetic genes and transcription factors were analyzed in flowers and throughout three fruit development stages. Flavonoid biosynthetic genes were developmentally regulated, showing a decrease in transcript levels during fruit maturation. A high degree of positive correlations between the content of targeted metabolites and the expression of biosynthetic genes indicated the transcriptional regulation of flavonoid biosynthesis during C. creticus fruit development. This is further supported by the high degree of significant positive correlations between the expression of biosynthetic genes and transcription factors. The results suggest that leucoanthocyanidin reductase predominates the biosynthetic pathway in the control of flavan-3-ol formation, which results in catechin and gallocatechin as two of the major building blocks for Cistus proanthocyanidins. Additionally, there is a decline in ethylene production rates during non-climacteric Cistus fruit maturation, which coincides with the downregulation of the majority of flavonoid- and ethylene-related biosynthetic genes and corresponding transcription factors as well as with the decline in flavonoid content. Finally, functional characterization of a Cistus flavonoid hydroxylase (F3'5'H) was performed for the first time.

Evaluating the influence of temperature on proanthocyanidin biosynthesis in developing grape berries (Vitis vinifera L.)

The variability in grape (Vitis vinifera L.) proanthocyanidin content is largely attributable to viticultural and environmental conditions. However, the particular effect temperature has on proanthocyanidin biosynthesis is poorly understood. The aim of the present study was to ascertain the magnitude of the effect of temperature on proanthocyanidin biosynthesis in Cabernet Sauvignon grape berries cultured in vitro. In addition, the effects of temperature on global gene transcription were evaluated, and the microarray data were later validated by quantitative real-time PCR (qPCR). The grape berries used in this research were sampled 3-4 weeks after full bloom and cultured in vitro either under a low (20 °C) or high (30 °C) temperature treatment for 15 days (d) with sampling occurring every five days. The proanthocyanidin content was higher in the skin and seeds of grape berries cultured at a low temperature compared with a high temperature. However, overall proanthocyanidin composition between the treatments was not significantly affected. Microarray data revealed a total of 1298 genes with ≥ 3.5-fold expression differences under high temperature conditions. High temperature also inhibited the expression level of key genes involved in proanthocyanidin biosynthesis, anthocyanidin reductase (ANR) and leucoanthocyanidin reductase-1 (LAR-1) within the berry skin. However, the transcriptomic accumulation of transcription factors, such as VvMybPAs, VvMyb5a and VvMyb5b, was barely influenced during the peak expression of ANR and LAR-1. Thus, the present study revealed that temperature has a significant effect on proanthocyanidin biosynthesis in grape during berry development through enhancing the expression of key biosynthetic genes.

PcDWF1, a pear brassinosteroid biosynthetic gene homologous to AtDWARF1, affected the vegetative and reproductive growth of plants

BACKGROUND

The steroidal hormones brassinosteroids (BRs) play important roles in plant growth and development. The pathway and genes involved in BR biosynthesis have been identified primarily in model plants like Arabidopsis, but little is known about BR biosynthesis in woody fruits such as pear.

RESULTS

In this study, we found that applying exogenous brassinolide (BL) could significantly increase the stem growth and rooting ability of Pyrus ussuriensis. PcDWF1, which had a significantly lower level of expression in the dwarf-type pear than in the standard-type pear, was cloned for further analysis. A phylogenetic analysis showed that PcDWF1 was a pear brassinosteroid biosynthetic gene that was homologous to AtDWARF1. The subcellular localization analysis indicated that PcDWF1 was located in the plasma membrane. Overexpression of PcDWF1 in tobacco (Nicotiana tabacum) or pear (Pyrus ussuriensis) plants promoted the growth of the stems, which was caused by a larger cell size and more developed xylem than those in the control plants, and the rooting ability was significantly enhanced. In addition to the change in vegetative growth, the tobacco plants overexpressing PcDWF1 also had a delayed flowering time and larger seed size than did the control tobacco plants. These phenotypes were considered to result from the higher BL contents in the transgenic lines than in the control tobacco and pear plants.

CONCLUSIONS

Taken together, these results reveal that the pear BR biosynthetic gene PcDWF1 affected the vegetative and reproductive growth of Pyrus ussuriensis and Nicotiana tabacum and could be characterized as an important BR biosynthetic gene in perennial woody fruit plants.

Comparative physiological, metabolomic, and transcriptomic analyses reveal developmental stage-dependent effects of cluster bagging on phenolic metabolism in Cabernet Sauvignon grape berries

BACKGROUND

Light conditions significantly influence grape berry ripening and the accumulation of phenolic compounds, but the underlying molecular basis remains partially understood. Here, we applied integrated transcriptomics and pathway-level metabolomics analyses to investigate the effect of cluster bagging during various developmental stages on phenolic metabolism in Cabernet Sauvignon grapes.

RESULTS

Bagging treatments had limited effects on berry quality attributes at harvest and did not consistently affect phenolic acid biosynthesis between seasons. Significantly elevated flavan-3-ol and flavonol contents were detected in re-exposed berries after bagging during early-developmental stages, while bagging after véraison markedly inhibited skin anthocyanin accumulation. Several anthocyanin derivatives and flavonol glycosides were identified as marker phenolic metabolites for distinguishing bagged and non-bagged grapes. Coordinated transcriptional changes in the light signaling components CRY2 and HY5/HYHs, transcription regulator MYBA1, and enzymes LAR, ANR, UFGT and FLS4, coincided well with light-responsive biosynthesis of the corresponding flavonoids. The activation of multiple hormone signaling pathways after both light exclusion and re-exposure treatments was inconsistent with the changes in phenolic accumulation, indicating a limited role of plant hormones in mediating light/darkness-regulated phenolic biosynthesis processes. Furthermore, gene-gene and gene-metabolite network analyses discovered that the light-responsive expression of genes encoding bHLH, MYB, WRKY, NAC, and MADS-box transcription factors, and proteins involved in genetic information processing and epigenetic regulation such as nucleosome assembly and histone acetylation, showed a high positive correlation with grape berry phenolic accumulation in response to different light regimes.

CONCLUSIONS

Altogether, our findings provide novel insights into the understanding of berry phenolic biosynthesis under light/darkness and practical guidance for improving grape features.