Tomato geranylgeranyl diphosphate synthase isoform 1 is involved in the stress-triggered production of diterpenes in leaves and strigolactones in roots

Carotenoids are photoprotectant pigments and precursors of hormones such as strigolactones (SL). Carotenoids are produced in plastids from geranylgeranyl diphosphate (GGPP), which is diverted to the carotenoid pathway by phytoene synthase (PSY). In tomato (Solanum lycopersicum), three genes encode plastid-targeted GGPP synthases (SlG1 to SlG3) and three genes encode PSY isoforms (PSY1 to PSY3). Here, we investigated the function of SlG1 by generating loss-of-function lines and combining their metabolic and physiological phenotyping with gene co-expression and co-immunoprecipitation analyses. Leaves and fruits of slg1 lines showed a wild-type phenotype in terms of carotenoid accumulation, photosynthesis, and development under normal growth conditions. In response to bacterial infection, however, slg1 leaves produced lower levels of defensive GGPP-derived diterpenoids. In roots, SlG1 was co-expressed with PSY3 and other genes involved in SL production, and slg1 lines grown under phosphate starvation exuded less SLs. However, slg1 plants did not display the branched shoot phenotype observed in other SL-defective mutants. At the protein level, SlG1 physically interacted with the root-specific PSY3 isoform but not with PSY1 and PSY2. Our results confirm specific roles for SlG1 in producing GGPP for defensive diterpenoids in leaves and carotenoid-derived SLs (in combination with PSY3) in roots

Diversity in melon flesh color: tools for genetic analysis

One of the processes that occur during melon fruit ripening is β-carotene accumulation, providing the characteristic orange flesh color of most of the cantalupensis cultivars. However, flesh color is one of the most variable traits in this species, and cultivars with dark to light orange, salmon, white, green or even yellow flesh also exist. The content in carotenoid compounds was measured in 90 different genotypes representing the diversity of the species. Total carotenoids were extracted from frozen melon fruit flesh and individual carotenoids were then separated by HPLC and quantified. The most abundant carotenoid was β-carotene. As it was expected, the orange colour of the fruit flesh from most cantalupensis coincided with the highest levels of β-carotene. Interestingly some Italian and French landraces had higher β-carotene amounts than commercial cultivars. Also significant amounts of other carotenoids, such as lutein and β-cryptoxanthin were found in these and other exotic accessions, belonging to the ameri and conomon groups. ß-caroten and ß-cryptoxanthin show provitamin A activity, and lutein plays a role in preventing macular degeneration. Therefore, this germplasm collection, comprising such variable accessions in caroteinoids content, represents a valuable reservoir to add nutritional value to the melon commercial cultivars. Most of the analyzed genotypes were resequenced recently and the population structure has been studied. SNPs in many genes involved in the carotenoids metabolic pathway are available today and further related studies can be performe

Signaling in the tomato immunity against fusarium oxysporum

New strategies of control need to be developed with the aim of economic and environmental sustainability in plant and crop protection. Metabolomics is an excellent platform for both understanding the complex plant–pathogen interactions and unraveling new chemical control strategies. GC-MS-based metabolomics, along with a phytohormone analysis of a compatible and incompatible interaction between tomato plants and Fusarium oxysporum f. sp. lycopersici, revealed the specific volatile chemical composition and the plant signals associated with them. The susceptible tomato plants were characterized by the over-emission of methyl-and ethyl-salicylate as well as some fatty acid derivatives, along with an activation of salicylic acid and abscisic acid signaling. In contrast, terpenoids, benzenoids, and 2-ethylhexanoic acid were differentially emitted by plants undergoing an incompatible interaction, together with the activation of the jasmonic acid (JA) pathway. In accordance with this response, a higher expression of several genes participating in the biosynthesis of these volatiles, such as MTS1, TomloxC, TomloxD, and AOS, as well as JAZ7, a JA marker gene, was found to be induced by the fungus in these resistant plants. The characterized metabolome of the immune tomato plants could lead to the development of new resistance inducers against Fusarium wilt treatment

Untargeted metabolomics of rind essential oils allowed to differentiate two closely related clementine varieties

Chemical characterization of clementine varieties (Citrus clementina Hort. ex Tan.) essential oils (EO) can lead to variety identification and valorization of their potential use in food and aroma industries. The goal of this study was the chemometric discrimination between two very closely related and morphologically identical clementine varieties, Clemenules (NL) and Clemen-pons (PO), based on their rind EO, to identify the differential volatile organic compounds (VOCs) and to determine their antioxidant capacity. EO rind volatile profile was determined by gas chro-matography coupled to mass spectrometry in Citrus fruit at different ripening stages grown two independent years in two different locations. Untargeted metabolomics and multivariate data analysis showed an evolution of EO volatile profiles markedly parallel in both varieties. Although EO qualitative composition was identical in both varieties, PLS‐DA allowed the identification of char-acteristic VOCs, quantitatively discriminating them along all the ripening process. PO showed higher accumulation of several mono‐ and sesquiterpene compounds such as trans‐carveol, while NL showed higher levels of aldehyde and alcohol non‐terpenoids like dodecanal. Both varieties evinced identical EO antioxidant activities, indicating a similar value for food preservation. Hence, untargeted metabolomics approach based on rind EO volatiles was revealed as a powerful tech-nique able to differentiate between morphologically undistinguishable Citrus varieties