Transcriptomics and metabolomics reveal the underlying mechanism of drought treatment on anthocyanin accumulation in postharvest blood orange fruit

BACKGROUND

Anthocyanins are the most important compounds for nutritional quality and economic values of blood orange. However, there are few reports on the pre-harvest treatment accelerating the accumulation of anthocyanins in postharvest blood orange fruit. Here, we performed a comparative transcriptome and metabolomics analysis to elucidate the underlying mechanism involved in seasonal drought (SD) treatment during the fruit expansion stage on anthocyanin accumulation in postharvest 'Tarocco' blood orange fruit.

RESULTS

Our results showed that SD treatment slowed down the fruit enlargement and increased the sugar accumulation during the fruit development and maturation period. Obviously, under SD treatment, the accumulation of anthocyanin in blood orange fruit during postharvest storage was significantly accelerated and markedly higher than that in CK. Meanwhile, the total flavonoids and phenols content and antioxidant activity in SD treatment fruits were also sensibly increased during postharvest storage. Based on metabolome analysis, we found that substrates required for anthocyanin biosynthesis, such as amino acids and their derivatives, and phenolic acids, had significantly accumulated and were higher in SD treated mature fruits compared with that of CK. Furthermore, according to the results of the transcriptome data and weighted gene coexpression correlation network analysis (WGCNA) analysis, phenylalanine ammonia-lyase (PAL3) was considered a key structural gene. The qRT-PCR analysis verified that the PAL3 was highly expressed in SD treated postharvest stored fruits, and was significantly positively correlated with the anthocyanin content. Moreover, we found that other structural genes in the anthocyanin biosynthesis pathway were also upregulated under SD treatment, as evidenced by transcriptome data and qRT-PCR analysis.

CONCLUSIONS

The findings suggest that SD treatment promotes the accumulation of substrates necessary for anthocyanin biosynthesis during the fruit ripening process, and activates the expression of anthocyanin biosynthesis pathway genes during the postharvest storage period. This is especially true for PAL3, which co-contributed to the rapid accumulation of anthocyanin. The present study provides a theoretical basis for the postharvest quality control and water-saving utilization of blood orange fruit.

Drought timing and species growth phenology determine intra-annual recovery of tree height and diameter growth

Droughts interact with tree phenology to drive declines in growth. As climate change makes drought more likely in the Northeastern USA, it is important to understand how droughts at different times of year will lead to reduced height and diameter growth of trees. To determine how seasonal drought may reduce intra-annual growth, we implemented spring, summer or fall droughts on 288 containerized saplings of six tree species (Acer rubrum, Betula papyrifera, Prunus serotina, Juniperus virginiana, Pinus strobus and Thuja occidentalis). We tracked weekly soil moisture, leaf water potential, height, diameter and survival of all trees before, during and after each 6-week drought. We found that the tree species that conducted the majority of their height or diameter growth in the spring were most sensitive to spring droughts (B. papyrifera and Pi. strobus). Thuja occidentalis also experienced significantly reduced growth from the spring drought but increased growth after the drought ended and achieved total height and diameter growth similar to controls. In contrast, summer droughts halted growth in most species for the remainder of the growing season even after the drought had ended. Fall droughts never impacted growth in the current year. These fine temporal-scale measurements of height and diameter growth suggest that tree response varies among species and is dynamic at intra-annual scales. These relatively rare data on intra-annual height growth sensitivity are important for canopy recruitment of saplings in forest ecosystems. Species-specific sensitivities of intra-annual growth to drought can inform models of forest competition in a changing climate.

Response of metabolic and lipid synthesis gene expression changes in Camellia oleifera to mulched ecological mat under drought conditions

Plants respond to adverse conditions by activating defense mechanisms that alter metabolism and impact agricultural crop yield. Organic mulching of Camellia oleifera leads to increased oil yield compared to control. In this study, multi-platform untargeted metabolomics and qRT-PCR were used to measure the effects of organic mulching on seed kernel metabolism. Metabolomics analysis revealed that tyrosine, tryptophan, and several flavonoids and polyphenol metabolites were significantly lower in the mulched treatment compared to the control, indicating lower stress levels with mulching. The qRT-PCR analysis showed that EAR, SAD, and CoHCD were up-regulated by mulching, while CT, FAD7, FAD8, CoATS1, SQS, SQE, FATB, and β-AS were down-regulated. Correlation network analysis was used to integrate data from this multi-omics investigation to analyze the relationships between differentially expressed genes, metabolites, and fruit and soil indicators concerning mulch treatment of C. oleifera.

Survival and growth of Virola surinamensis yearlings: Water augmentation in gap and understory

Factors affecting seedling Virola surinamensis (Myristicaceae) survival and growth were investigated on Barro Colorado Island, Panama. Seedlings planted 3 months after germination were monitored in treefall gaps and understory using 2.25 ha irrigated and control plots through the first dry season. During the dry season, irrigated plants in gaps increased total leaf area significantly more than did irrigated plants in the shaded understory. Over the same dry season, control plants in gaps and in the shaded understory lost similar amounts of leaf area. Seedlings in understory were suppressed in stem height and biomass in both irrigated and control plots; these measures were greater in gaps and greatest in irrigated gaps (height). Roots were similar in length in all treatments, but greater in biomass in gaps than understory due to greater proliferation of secondary roots in control and irrigated gaps than in control and irrigated understory. This experiment demonstrates both water and light limitation during the first dry season after germination. V. surinamensis seedlings are capable of survival and modest growth of leaf area in the deep shade of the understory in moist locations; they are severely disadvantaged in shaded understory subject to drought, where most seeds fall and most seedlings establish. The broken canopy of a gap allows shoot and consequently root growth that permits seedlings to survive seasonal drought.