Genome-wide QTL analysis of tomato fruit cuticle deposition and composition

Genetics of traits related to fruit cuticle deposition and composition was studied in two red-fruited tomato species.Two mapping populations derived from the cross between the cultivated tomato(Solanum lycopersicum L.)and its closest relative wild species Solanum pimpinellifolium L.were employed to conduct a QTL analysis.A combination of fruit cuticle deposition,components and anatomical traits were investigated and the individual effect of each QTL evaluated.A total of 70 QTLs were identified,indicating that all the cuticle traits analyzed have a complex polygenic nature.A combination of additive and epistatic interactions was observed for all the traits,with positive contribution of both parental lines to most of them.Colocalization of QTLs for various traits uncovered novel genomic regions producing extensive changes in the cuticle.Cuticle density emerges as an important trait since it can modulate cuticle thickness and invagination thus providing a strategy for sustaining mechanical strength without compromising palatability.Two genomic regions,located in chromosomes 1 and 12,are responsible for the negative interaction between cuticle waxes and phenolics identified in tomato fruit.Several candidate genes,including transcription factors and structural genes,are postulated and their expression analyzed throughout development.

Down-regulation of Fra a 1.02 in strawberry fruits causes transcriptomic and metabolic changes compatible with an altered defense response

The strawberry Fra a 1 proteins belong to the class 10 Pathogenesis-Related(PR-10)superfamily.In strawberry,a large number of members have been identified,but only a limited number is expressed in the fruits.In this organ,Fra a 1.01 and Fra a 1.02 are the most abundant Fra proteins in the green and red fruits,respectively,however,their function remains unknown.To know the function of Fra a 1.02 we have generated transgenic lines that silence this gene,and performed metabolomics,RNA-Seq,and hormonal assays.Previous studies associated Fra a 1.02 to strawberry fruit color,but the analysis of anthocyanins in the ripe fruits showed no diminution in their content in the silenced lines.Gene ontology(GO)analysis of the genes differentially expressed indicated that oxidation/reduction was the most represented biological process.Redox state was not apparently altered since no changes were found in ascorbic acid and glutathione(GSH)reduced/oxidized ratio,but GSH content was reduced in the silenced fruits.In addition,a number of glutathione-S-transferases(GST)were down-regulated as result of Fra a 1.02-silencing.Another highly represented GO category was transport which included a number of ABC and MATE transporters.Among the regulatory genes differentially expressed WRKY33.1 and WRKY33.2 were down-regulated,which had previously been assigned a role in strawberry plant defense.A reduced expression of the VQ23 gene and a diminished content of the hormones JA,SA,and IAA were also found.These data might indicate that Fra a 1.02 participates in the defense against pathogens in the ripe strawberry fruits.

The Strawberry Fruit Fra a Allergen Functions in Flavonoid Biosynthesis

The strawberry Fra a I allergen is a homolog of the major birch pollen allergen Bet v 1. It is synthesized by red ripe fruits of Fragaria x ananassa while white fruits of a mutant genotype, which is known to be tolerated by individuals affected by allergy, are devoid of it. Proteomic analyses have shown that Fra a 1 is down-regulated in the tolerated white- fruited genotype along with enzymes of the anthocyanin pigment pathway. In this study, we report the spatial and tem- poral expression of three Fra a genes that encode different isoforms, and the transient RNAi-mediated silencing of the Fra a genes in strawberry fruits of the red-fruited cultivar Elsanta with an ihpRNA construct. As a consequence of reduced levels of Fra a mRNAs, fruits were obtained that produced significantly decreased levels of anthocyanins and upstream metabolites. This effect is consistent with the parallel down-regulation of the phenylalanine ammonia lyase （FaPAL） and to a lesser extent of the chalcone synthase （FaCHS） transcript levels also found in these fruits. In naturally occurring white- fruited genotypes of F. chiloensis and F. vesca, Fra a transcript levels are higher than those of the red-fruited varieties, likely to compensate for the low expression levels of FaPAL and FaCHS in these mutant genotypes. The results demonstrate that Fra a expression is directly linked to flavonoid biosynthesis and show that the Fra a allergen has an essential biological function in pigment formation in strawberry fruit.

Analysis of the Interface between Primary and Secondary Metabolism in Catharanthus roseus Cell Cultures Using ^13C-Stable Isotope Feeding and Coupled Mass Spectrometry

Dear Editor, The tropical plant Madagascar periwinkle Catharanthus roseus （L.） G.Don is a rich source of plant-derived medicinal ter-penoid indole alkaloids （TIAs）, including the anti-hypertensive ajmalicine, the sedative compound serpentine, and the anti-cancer drugs vinblastine and vincristine. However, the latter two compounds are produced in C. roseus plants only in very low amounts. Elicitors such as hormones （e.g. jasmonates or salicylic acid） activate plant natural defense responses, includ-ing increased secondary metabolite production （EI-Sayed and Verpoorte, 2007; Lackman et al.. 2011）.