Decoding altitude-activated regulatory mechanisms occurring during apple peel ripening

Apple(Malus domestica Borkh)is an important fruit crop cultivated in a broad range of environmental conditions.Apple fruit ripening is a physiological process,whose molecular regulatory network response to different environments is still not sufficiently investigated and this is particularly true of the peel tissue.In this study,the influence of environmental conditions associated with low(20 m)and high(750 m)altitude on peel tissue ripening was assessed by physiological measurements combined with metabolomic and proteomic analyses during apple fruit development and ripening.Although apple fruit ripening was itself not affected by the different environmental conditions,several key color parameters,such as redness and color index,were notably induced by high altitude.Consistent with this observation,increased levels of anthocyanin and other phenolic compounds,including cyanidin-3-O-galactoside,quercetin-3-O-rhamnoside,quercetin-3-O-rutinoside,and chlorogenic acid were identified in the peel of apple grown at high altitude.Moreover,the high-altitude environment was characterized by elevated abundance of various carbohydrates(e.g.,arabinose,xylose,and sucrose)but decreased levels of glutamic acid and several related proteins,such as glycine hydroxymethyltransferase and glutamate–glyoxylate aminotransferase.Other processes affected by high altitude were the TCA cycle,the synthesis of oxidative/defense enzymes,and the accumulation of photosynthetic proteins.From the obtained data we were able to construct a metabolite-protein network depicting the impact of altitude on peel ripening.The combined analyses presented here provide new insights into physiological processes linking apple peel ripening with the prevailing environmental conditions.

Synthetic biology identifies the minimal gene set required for paclitaxel biosynthesis in a plant chassis

The diterpenoid paclitaxel(Taxol)is a chemotherapy medication widely used as a first-line treatment against several types of solid cancers.The supply of paclitaxel from natural sources is limited.However,missing knowledge about the genes involved in several specific metabolic steps of paclitaxel biosynthesis has rendered it difficult to engineer the full pathway.In this study,we used a combination of transcriptomics,cell biology,metabolomics,and pathway reconstitution to identify the complete gene set required for the heterologous production of paclitaxel.We identified the missing steps from the current model of paclitaxel biosynthesis and confirmed the activity of most of the missing enzymes via heterologous expression in Nicotiana benthamiana.Notably,we identified a new C4β-C20 epoxidase that could overcome the first bottleneck of metabolic engineering.We used both previously characterized and newly identified oxomutases/epoxidases,taxane 1β-hydroxylase,taxane 9aα-hydroxylase,taxane 9α-dioxygenase,and phenylalanine-CoA ligase,to successfully biosynthesize the key intermediate baccatin Ill and to convert baccatin Ill into paclitaxel in N.benthamiana.In combination,these approaches establisha metabolic route to taxoidbiosynthesis and provide insights into the unique chemistry that plants use to generate complex bioactive metabolites.

Exploiting Natural Variation in Tomato to Define Pathway Structure and Metabolic Regulation of Fruit Polyphenolics in the Lycopersicum Complex

While the structures of plant primary metabolic pathways are generally well defined and highly conserved across species,those defining specialized metabolism are less well characterized and more highly variable across species.In this study,we investigated polyphenolic metabolism in the lycopersicum complex by characterizing the underlying biosynthetic and decorative reactions that constitute the metabolic network of polyphenols across eight different species of tomato.For this purpose,GC-MS-and LC-MS-based metabolomics of different tissues of Solatium lycopersicum and wild tomato species were carried out,in concert with the evaluation of cross-hybridized microarray data for MapMan-based transcriptomic analysis,and publicly available RNA-sequencing data for annotation of biosynthetic genes.The combined data were used to compile species-specific metabolic networks of polyphenolic metabolism,allowing the establishment of an entire pan-species biosynthetic framework as well as annotation of the functions of decoration enzymes involved in the formation of metabolic diversity of the flavonoid pathway.The combined results are discussed in the context of the current understanding of tomato flavonol biosynthesis as well as a global view of metabolic shifts during fruit ripening.Our results provide an example as to how large-scale biology approaches can be used for the definition and refinement of large specialized metabolism pathways.

The genomes of Taxus species unveil novel candidates in the biosynthesis of taxoids

Taxaceae is the yew family of conifers and includes evergreen trees and small shrubs mainly distributed in Eurasia and North America.The genus of Taxus has attracted considerable attention since Monroe E.Wall and Mansukh C.Wani firstly isolated and characterized an unusual cyclic diterpenoid from the bark of the Pacific yew tree(Wani et al.,1971).This compound,subsequently called paclitaxel,was shown to promote tubulin assembly into microtubules,preventing their disassembly.Subsequently,paclitaxel was approved for medical use against ovarian cancer in 1992(Fischer and Ganellin,2010).