Metabolite profiling characterises chemotypes of Musa diploids and triploids at juvenile and preflowering growth stages

Open Access Journal; Published online: 15 March 2019Bananas (Musa spp.) are consumed worldwide as dessert and cooking types. Edible banana varieties are for the most part seedless and sterile and therefore vegetatively propagated. This confers difficulties for breeding approaches against pressing biotic and abiotic threats and for the nutritional enhancement of banana pulp. A panel of banana accessions, representative of the diversity of wild and cultivated bananas, was analysed to assess the range of chemotypes available globally. The focus of this assessment was banana leaves at two growth stages (juvenile and pre-flowering), to see when during the plant growth metabolic differences can be established. The metabolic data corresponded to genomic trends reported in previous studies and demonstrated a link between metabolites/pathways and the genomes of M. acuminata and M. balbisiana. Furthermore, the vigour and resistance traits of M. balbisiana was connected to the phenolic composition and showed differences with the number of B genes in the hybrid accessions. Differences in the juvenile and pre-flowering data led to low correlation between the growth stages for prediction purposes

Inactivation of rice starch branching enzyme IIb triggers broad and unexpected changes in metabolism by transcriptional reprogramming

Starch properties can be modified by mutating genes responsible for the synthesis of amylose and amylopectin in the endosperm. However, little is known about the effects of such targeted modifications on the overall starch biosynthesis pathway and broader metabolism. Here we investigated the effects of mutating the OsSBEIIb gene encoding starch branching enzyme IIb, which is required for amylopectin synthesis in the endosperm. As anticipated, homozygous mutant plants, in which OsSBEIIb was completely inactivated by abolishing the catalytic center and C-terminal regulatory domain, produced opaque seeds with depleted starch reserves. Amylose content in the mutant increased from 19.6 to 27.4% and resistant starch (RS) content increased from 0.2 to 17.2%. Many genes encoding isoforms of AGPase, soluble starch synthase, and other starch branching enzymes were up-regulated, either in their native tissues or in an ectopic manner, whereas genes encoding granule-bound starch synthase, debranching enzymes, pullulanase, and starch phosphorylases were largely down-regulated. There was a general increase in the accumulation of sugars, fatty acids, amino acids, and phytosterols in the mutant endosperm, suggesting that intermediates in the starch biosynthesis pathway increased flux through spillover pathways causing a profound impact on the accumulation of multiple primary and secondary metabolites. Our results provide insights into the broader implications of perturbing starch metabolism in rice endosperm and its impact on the whole plant, which will make it easier to predict the effect of metabolic engineering in cereals for nutritional improvement or the production of valuable metabolites.We would like to acknowledge funding from Ministry of Economy and Competitiveness, Spain (RTI2018-097613-BI00 to C.Z., PGC2018-097655-B-I00 to P.C., and AGL2017-85377-R to T.C.); Generalitat de Catalunya Grant 2017 SGR 828 to the Agricultural Biotechnology and Bioeconomy Unit; and the European Union Framework Program DISCO (from discovery to final products: a next-generation pipeline for the sustainable generation of high-value plant products; Project 613513) to P.D.F

The coordinated upregulated expression of genes involved in MEP, chlorophyll, carotenoid and tocopherol pathways, mirrored the corresponding metabolite contents in rice leaves during de-etiolation

Light is an essential regulator of many developmental processes in higher plants. We investigated the effect of 4-hydroxy-3-methylbut-2-enyl diphosphate reductase 1/2 genes (OsHDR1/2) and isopentenyl diphosphate isomerase 1/2 genes (OsIPPI1/2) on the biosynthesis of chlorophylls, carotenoids, and phytosterols in 14-day-old etiolated rice (Oyza sativa L.) leaves during de-etiolation. However, little is known about the effect of isoprenoid biosynthesis genes on the corresponding metabolites during the de-etiolation of etiolated rice leaves. The results showed that the levels of α-tocopherol were significantly increased in de-etiolated rice leaves. Similar to 1-deoxy-D-xylulose-5-phosphate synthase 3 gene (OsDXS3), both OsDXS1 and OsDXS2 genes encode functional 1-deoxy-D-xylulose-5-phosphate synthase (DXS) activities. Their expression patterns and the synthesis of chlorophyll, carotenoid, and tocopherol metabolites suggested that OsDXS1 is responsible for the biosynthesis of plastidial isoprenoids in de-etiolated rice leaves. The expression analysis of isoprenoid biosynthesis genes revealed that the coordinated expression of the MEP (2-C-methyl-D-erythritol 4-phosphate) pathway, chlorophyll, carotenoid, and tocopherol pathway genes mirrored the changes in the levels of the corresponding metabolites during de-etiolation. The underpinning mechanistic basis of coordinated light-upregulated gene expression was elucidated during the de-etiolation process, specifically the role of light-responsive cis-regulatory motifs in the promoter region of these genes. In silico promoter analysis showed that the light-responsive cis-regulatory elements presented in all the promoter regions of each light-upregulated gene, providing an important link between observed phenotype during de-etiolation and the molecular machinery controlling expression of these genesThis research was funded by Gansu Provincial Key Laboratory of Aridland Crop Science, Gansu Agricultural University (Project No. GSCS-2020-07); The National Natural Science Foundation of China (31870278); the Spanish Ministry of Economy and Competitiveness (MINECO), Spain (RTI2018-097613-B-I00; PGC2018-097655-B-I00); in part by the European Union Framework Pro- gram DISCO (613513) “from DISCOvery to products: a next-generation pipeline for the sustainable generation of high-value plant products”, the European Cooperation in Science and Technology project EUROCAROTEN (OC-2015-1-19780), Generalitat de Catalunya Grant 2017 SGR 828 to the Agricultural Biotechnology and Bioeconomy Unit (ABBU), and the International Science and Technol- ogy Cooperation Project 20190201013JC (from Jilin Provincial Science and Technology Department, China); GAU-KYQD-2019-06, Gansu Agricultural University