Abstract:

Pectin is a main component of cell wall and the most complex family of polysaccharides in nature. Its composition is essential for the normal growth and morphology pattern, as demonstrated by pectin-defective mutant phenotypes. Besides this basic role in plant physiology, in tomato, pectin structure contributes to very important quality traits such as fruit firmness. Sixty seven different enzymatic activities have been sugested to be required for pectin biosynthesis but only a few genes have been identified and studied so far. In this work we characterized the tomato galacturonosyltransferase family and performed a detailed functional study of the GAUT4 gene. The tomato genome harbors all orthologous genes to those previously described in A. thaliana and a transcriptional profile revealed that the GAUT4 gene is expressed at higher levels in developing organs. GAUT4 silenced tomato plants exhibited an increment in vegetative biomass associated with the palisade parenchyma enlargement. Silenced fruits showed an altered pectin composition, accumulated less starch along with reduced amount of pectin that coincided with an increase in firmness. Moreover, harvest index was dramatically reduced as a consequence of reduction in the fruit weight and number. Altogether, these results suggest that, beyond its role in pectin biosynthesis, GAUT4 interferes with carbon metabolism, partitioning and allocation. Hence, this cell wall-related gene seems to be key in determining plant growth and fruit production in tomato.

Author affiliation: de Godoy, Fabiana. Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Bermudez, Luisa. Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Silvestre, Bruno Lira. Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Souza, Amanda Pereira de . Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Elbl, Paula. Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Demarco, Diego. Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Alseekh, Saleh. Max Planck Institute for Molecular Plant Physiology; Alemania

Author affiliation: Insani, Marina. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigación de Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina

Author affiliation: Buckeridge, Marcos. Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Almeida, Juliana. Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Grigioni, Gabriela Maria. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigación de Agroindustrias. Instituto de Tecnología de Alimentos; Argentina

Author affiliation: Fernie, Alisdair Robert. Max Planck Institute for Molecular Plant Physiology; Alemania

Author affiliation: Carrari, Fernando Oscar. Instituto Nacional de Tecnología Agropecuaria. Centro Nacional de Investigaciones Agropecuarias. Centro de Investigación de Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Rossi, Maria Magdalena. Universidade de São Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Abstract:

Pectin is a main component of the plant cell wall and is the most complex family of polysaccharides in nature. Its composition is essential for the normal growth and morphology pattern, as demonstrated by pectin-defective mutant phenotypes. Besides this basic role in plant physiology, in tomato, pectin structure contributes to very important quality traits such as fruit firmness. Sixty-seven different enzymatic activities have been suggested to be required for pectin biosynthesis, but only a few genes have been identified and studied so far. This study characterized the tomato galacturonosyltransferase (GAUT) family and performed a detailed functional study of the GAUT4 gene. The tomato genome harbours all genes orthologous to those described previously in Arabidopsis thaliana, and a transcriptional profile revealed that the GAUT4 gene was expressed at higher levels in developing organs. GAUT4-silenced tomato plants exhibited an increment in vegetative biomass associated with palisade parenchyma enlargement. Silenced fruits showed an altered pectin composition and accumulated less starch along with a reduced amount of pectin, which coincided with an increase in firmness. Moreover, the harvest index was dramatically reduced as a consequence of the reduction in the fruit weight and number. Altogether, these results suggest that, beyond its role in pectin biosynthesis, GAUT4 interferes with carbon metabolism, partitioning, and allocation. Hence, this cell-wall-related gene seems to be key in determining plant growth and fruit production in tomato

Author affiliation: Godoy, Fabiana de. Universidade de São Pablo. Departamento de Botânica; Brasil

Author affiliation: Bermúdez, Luisa. Universidade de São Pablo. Departamento de Botânica; Brasil

Author affiliation: Lira, Bruno Silvestre. Universidade de São Pablo. Departamento de Botânica; Brasil

Author affiliation: Souza, Amanda Pereira de. Universidade de São Pablo. Departamento de Botânica; Brasil

Author affiliation: Elbl, Paula. Universidade de São Pablo. Departamento de Botânica; Brasil

Author affiliation: Demarco, Diego. Universidade de São Pablo. Departamento de Botânica; Brasil

Author affiliation: Alseekh, Saleh. Max Planck Institute for Molecular Plant Physiology; Alemania

Author affiliation: Insani, Ester Marina. INTA. Instituto de Biotecnología; Argentina

Author affiliation: Buckeridge, Marcos. Universidade de São Pablo. Departamento de Botânica; Brasil

Author affiliation: Almeida, Juliana. Universidade de São Pablo. Departamento de Botânica; Brasil

Author affiliation: Grigioni, Gabriela Maria. INTA. Instituto de Tecnología de Alimentos; Argentina

Author affiliation: Fernie, Alisdair Robert. Max Planck Institute for Molecular Plant Physiology; Alemania

Author affiliation: Carrari, Fernando. INTA. Instituto de Biotecnología; Argentina

Author affiliation: Rossi, Magdalena. Universidade de São Pablo. Departamento de Botânica; Brasil

Abstract:

With the aim of determining the genetic basis of metabolic regulation in tomato fruit, we constructed a detailed physical map of genomic regions spanning previously described metabolic quantitative trait loci of a Solanum pennellii introgression line population. Two genomic libraries from S. pennellii were screened with 104 colocated markers from five selected genomic regions, and a total of 614 bacterial artificial chromosome (BAC)/cosmids were identified as seed clones. Integration of sequence data with the genetic and physical maps of Solanum lycopersicum facilitated the anchoring of 374 of these BAC/ cosmid clones. The analysis of this information resulted in a genome-wide map of a nondomesticated plant species and covers 10% of the physical distance of the selected regions corresponding to approximately 1% of the wild tomato genome. Comparative analyses revealed that S. pennellii and domesticated tomato genomes can be considered as largely colinear. A total of 1,238,705 bp from both BAC/cosmid ends and nine large insert clones were sequenced, annotated, and functionally categorized. The sequence data allowed the evaluation of the level of polymorphism between the wild and cultivated tomato species. An exhaustive microsynteny analysis allowed us to estimate the divergence date of S. pennellii and S. lycopersicum at 2.7 million years ago. The combined results serve as a reference for comparative studies both at the macrosyntenic and microsyntenic levels. They also provide a valuable tool for fine-mapping of quantitative trait loci in tomato. Furthermore, they will contribute to a deeper understanding of the regulatory factors underpinning metabolism and hence defining crop chemical composition. © 2010 American Society of Plant Biologists.

Author affiliation: Kamenetzky, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina

Author affiliation: Asis, Ramón. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina

Author affiliation: Bassi, Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina

Author affiliation: de Godoy, Fabiana. Universidade de Sao Paulo; Brasil

Author affiliation: Bermúdez, Luisa. Universidade de Sao Paulo; Brasil

Author affiliation: Fernie, Alisdair R.. Max Planck Institute for Molecular Plant Physiology; Alemania

Author affiliation: van Sluys, Marie Anne. Universidade de Sao Paulo; Brasil

Author affiliation: Vrebalov, Julia. Cornell University; Estados Unidos

Author affiliation: Giovannoni, James J.. Cornell University; Estados Unidos

Author affiliation: Rossi, Magdalena. Universidade de Sao Paulo; Brasil

Author affiliation: Carrari, Fernando Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina

Abstract:

Tocopherols, compounds with vitamin E (VTE) activity, are potent lipid-soluble antioxidants synthesized only by photosynthetic organisms. Their biosynthesis requires the condensation of phytyl-diphosphate and homogentisate, derived from the methylerythritol phosphate (MEP) and shikimate pathways (SK), respectively. These metabolic pathways are central in plant chloroplast metabolism and are involved in the biosynthesis of important molecules such as chlorophyll, carotenoids, aromatic amino-acids and prenylquinones. In the last decade, few studies have provided insights into the regulation of VTE biosynthesis and its accumulation. However, the pathway regulatory mechanism/s at mRNA level remains unclear. We have recently identified a collection of tomato genes involved in tocopherol biosynthesis. In this work, by a dedicated qPCR array platform, the transcript levels of 47 genes, including paralogs, were determined in leaves and across fruit development. Expression data were analyzed for correlation with tocopherol profiles by coregulation network and neural clustering approaches. The results showed that tocopherol biosynthesis is controlled both temporally and spatially however total tocopherol content remains constant. These analyses exposed 18 key genes from MEP, SK, phytol recycling and VTE-core pathways highly associated with VTE content in leaves and fruits. Moreover, genomic analyses of promoter regions suggested that the expression of the tocopherol-core pathway genes is trancriptionally coregulated with specific genes of the upstream pathways. Whilst the transcriptional profiles of the precursor pathway genes would suggest an increase in VTE content across fruit development, the data indicate that in the M82 cultivar phytyl diphosphate supply limits tocopherol biosynthesis in later fruit stages. This is in part due to the decreasing transcript levels of geranylgeranyl reductase (GGDR) which restricts the isoprenoid precursor availability. As a proof of concept, by analyzing a collection of Andean landrace tomato genotypes, the role of the pinpointed genes in determining fruit tocopherol content was confirmed. The results uncovered a finely tuned regulation able to shift the precursor pathways controlling substrate influx for VTE biosynthesis and overcoming endogenous competition for intermediates. The whole set of data allowed to propose that 1-deoxy-D-xylulose-5-phosphate synthase and GGDR encoding genes, which determine phytyl-diphosphate availability, together with enzyme encoding genes involved in chlorophyll-derived phytol metabolism appear as the most plausible targets to be engineered aiming to improve tomato fruit nutritional value.

Instituto de Biotecnología

Author affiliation: Quadrana, Leandro Daniel. INTA. Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Author affiliation: Almeida de Souza, Juliana Beatriz. Universidade de Sao Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Otaiza, Santiago N. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina

Author affiliation: Duffy, Tomás. INTA. Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.

Author affiliation: Silva, Junia V. Corrêa da. Universidade de Sao Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Godoy, Fabiana de. Universidade de Sao Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Asis, Ramón. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina

Author affiliation: Bermúdez, Luisa. Universidade de Sao Paulo. Instituto de Biociências. Departamento de Botânica; Brasil

Author affiliation: Fernie, Alisdair R. Max Planck Institute for Molecular Plant Physiology; Alemania

Author affiliation: Carrari, Fernando Oscar. INTA. Instituto de Biotecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.

Author affiliation: Rossi, Magdalena. Universidade de São Pablo. Instituto de Biociências. Departamento de Botânica; Brasil