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Knowledge about quantitative and qualitative characterization of phytochemical contents in Asteraceae leafy vegetables is continuously increasing due to the strong interest from scientists and consumers. This chapter deals with leafy vegetables of Lactuca sativa, Cichorium intybus and C. endivia species, given their relevance within the botanical family. It gives an overview of the wide differences occurring in genotype panels, in bioactive compound types and levels, focusing on phenolics, carotenoids and sesquiterpenes lactones. It also provides information on their biosynthesis pathways in plants together with health effects, bioaccessibility and bioavailability of diverse phytonutrient classes. Finally, it outlines the effects of the main pre-harvest and post-harvest factors affecting the amount and status of final products intended for dietary intake, and reports on some genetic aspects and biotechnologies aimed to biofortification of these species.

Doctorate Research in Plant Biology,XX Ciclo a.a.2003-2006 Università della Calabria

Doctorate Research in Plant Biology,XX Ciclo a.a.2003-2006

Leaves are specialized organs characterized by defined developmental destiny and determinate growth. The overexpression of Knotted1-like homeobox genes in different species has been shown to alter leaf shape and development, but a definite role for this class of genes remains to be established. Transgenics that overexpress Knotted1-like genes present some traits that are characteristic of altered cytokinin physiology. Here we show that lettuce (Lactuca sativa) leaves that overexpress KNAT1, an Arabidopsis kn1-like gene, acquire characteristics of indeterminate growth typical of the shoot and that this cell fate change is associated with the accumulation of specific types of cytokinins. The possibility that the phenotypic effects of KNAT1 overexpression may arise primarily from the modulation of local ratios of different cytokinins is discussed.

Endives (Cichorium endivia L.) are popular vegetables, diversified into curly/frisée- and smooth/broad-leafed (escaroles) cultivar types (cultigroups), and consumed as fresh and bagged salads. They are rich in sesquiterpene lactones (STL) that exert proven function on bitter taste and human health. The assembly of a reference transcriptome of 77,022 unigenes and RNA-sequencing experiments were carried out to characterize the differences between endives and escaroles at the gene structural and expression levels. A set of 3177 SNPs distinguished smooth from curly cultivars, and an SNP-supported phylogenetic tree separated the cultigroups into two distinct clades, consistently with the botanical varieties of origin (crispum and latifolium, respectively). A pool of 699 genes maintained differential expression pattern (core-DEGs) in pairwise comparisons between curly vs smooth cultivars grown in the same environment. Accurate annotation allowed the identification of 26 genes in the sesquiterpenoid biosynthesis pathway, which included several germacrene A synthase, germacrene A oxidase and costunolide synthase members (GAS/GAO/COS module), required for the synthesis of costunolide, a key precursor of lactucopicrin- and lactucin-like sesquiterpene lactones. The core-DEGs contained a GAS gene (contig83192) that was positively correlated with STL levels and recurrently more expressed in curly than smooth endives, suggesting a cultigroup-specific behavior. The significant positive correlation of GAS/GAO/COS transcription and STL abundance (2.4-fold higher in frisée endives) suggested that sesquiterpenoid pathway control occurs at the transcriptional level. Based on correlation analyses, five transcription factors (MYB, MYB-related and WRKY) were inferred to act on contig83192/GAS and specific STL, suggesting the occurrence of two distinct routes in STL biosynthesis., Diving into the genetics of endives Genetic analyses show molecular differences that could explain why curly endives taste bitterer than smooth ones. Donato Giannino of the Institute of Agricultural Biology and Biotechnology and colleagues in Italy analyzed the genetic differences between curly and smooth endives, a leafy vegetable used in salads. They found more than 3000 single sequence variations in genes distinguishing the two types from each other. Twenty six genes were involved in the biosynthesis of sesquiterpenoids, metabolites important for plant survival that also contribute to the bitter taste of endives and have antimalarial, sedative and analgesic effects when isolated for humans. Their levels were higher in curly than in smooth endives, potentially contributing to their more bitter taste. The information expands the genetic data available on endives for breeding programs.

Stem-chicory of the "Catalogna" group is a vegetable consumed for bitter-flavored stems. Type and levels of bitter sesquiterpene lactones (STLs) participate in conferring bitterness in vegetables. The content of lactucin--and lactucopocrin-like STLs was higher in "Molfettese" than "Galatina" landrace stalks, regardless of the cultivation sites, consistently with bitterness scores and gustative differences. The "Galatina" transcriptome assembly resulted in 58,872 unigenes, 77% of which were annotated, paving the way to molecular investigation of the STL pathway. Comparative transcriptome analysis allowed the identification of 69,352 SNPs and of 1640 differentially expressed genes that maintained the pattern independently of the site. Enrichment analyses revealed that 4 out of 29 unigenes were up-regulated in "Molfettese" vs "Galatina" within the sesquiterpenoid pathway. The expression of two germacrene A -synthase (GAS) and one -oxidase (GAO) genes of the costunolide branch correlated positively with the contents of lactucin-like molecules, supporting that STL biosynthesis regulation occurs at the transcriptional level. Finally, 46 genes encoding transcription factors (TFs) maintained a differential expression pattern between the two varieties regardless of the growth site; correlation analyses among TFs, GAS, GAO gene expressions and STLs contents suggest that one MYB and one bHLH may act in the pathway.