Isolamento de cDNAs parciais de quatro genes do metabolismo de carboidratos e analise de seus padrões de expressão durante a fase inicial do desenvolvimento de plantulas de jatoba (Hymenaea courbaril L.)

Aline Dias Brandão

Author(s):	Aline Dias Brandão Total Authors: 1
Document type:	Doctoral Thesis
Press:	Campinas, SP. , ilustrações.
Institution:	Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
Defense date:	2008-02-27
Examining board members:	Marcos Silveira Buckeridge; Helaine Carrer; Eduardo Purgatto; Marília Gaspar Mais; Antonio Vargas de Oliveira Figueira
Advisor:	Michel Georges Albert Vincentz; Marcos Silveira Buckeridge
Field of knowledge:	Biological Sciences - Genetics
Indexed in:	Base Acervus-UNICAMP; Biblioteca Digital da UNICAMP
Location:	Universidade Estadual de Campinas. Biblioteca Central Cesar Lattes; T/UNICAMP; B733i; Universidade Estadual de Campinas. Biblioteca do Instituto de Biologia; T/UNICAMP; B733i
Abstract
The jatobas (species belonging to the genus Hymenaea, family Leguminosae) display large physiological plasticity and as a consequence they have great adaptive capacity to several habitats. Different species and varieties of jatobas have adapted practically to all Brazilian tropical biomes, including the Amazon Forest and the complex of ecosystems that is formed by the Atlantic Forest, the Savannah and the Caatinga. Species of this genus contain xyloglucan as the main storage of carbon in their seeds. Xyloglucan is a polysaccharide similar to cellulose, but water soluble due to the branching with xylose and galactose. After germination, xyloglucan is completely degraded, producing free monosaccharides that are quickly metabolized to sucrose. The production of xyloglucan hydrolytic enzymes in the cotyledons is known to be controlled by auxin that comes from the shoot. However, it is not known how the mecanism is controlled. The aim of the present work was isolate partial cDNAs of the genes b-galactosidase (BGAL) and xyloglucan endo-transglycosylase or endo-b-1,4-glucanase (XET) xyloglucan degradation genes and two other genes related to sucrose metabolism (neutral/alkaline invertase - NI/AI and sucrose synthase - SUS) in order to try to evaluate possible forms of control of gene expression involved in the catabolism of xyloglucan in cotyledons of Hymenaea courbaril . Primers were designed on the basis of extant sequences obtained from databases for all genes. We guided the search by sequences obtained from species of the Leguminosae. We cloned partial sequences of genes coding BGAL, XTH, NI and SUS. Semi-quantitative RT-PCR (semi-quantitative reverse transcription-polimerase chain reaction) was used to analyze expression at the 45th day after imbibition (when the rate of mobilization is maximal) in cotyledons, leaves, hypocotyls and roots every 6 hours during 24 hours. The experimental treatments were 1) seedlings grown under natural conditions; II) seedlings with top shoot excised; III) seedlings treated with auxin transport inhibitor (NPA ¿ naphtyl phtalamic acid); IV) seedilings grown in continous light and V) seedilings grown in darkness. We observed that there are three mechanisms of response to auxin. In cotyledons the genes related to xyloglucan degradation, BGAL1 and XTH1, showed responses by auxin and light in the plant. The genes related to sucrose metabolism, AlkIN1 and SUS1, have shown responses to carbon flux. In leaves, hypocotyls and roots the gene pattern change according carbon source comes from product of storage xyloglucan degradation in cotyledons. Our results revealed the first description of cDNA isolation and allow characterize pattern of genes involved native Brazilian tree species establishment. Our results and enzymatic data obtained by other researchers suggest a transcriptional control of storage mobilization in jatoba. From the sequencing data, it was also possible to observe that neutral invertase (NI) gene cloned from roots of jatoba contains aminoacid residues that characterise the NI as an alkaline invertase (AlkIN1) instead. Based in degradation and mobilization of xyloglucan storage in cotyledons we propose an expression control model for ß-galactosidase, XTH, alkaline invertase and sucrose synthase in all analyzed tissues during early development in seedilings of Hymenaea courbaril by endogenous auxin influence and light alternance (AU)

FAPESP's process:	04/10159-8 - Control of the genetic expression of the metabolism of carbohydrates by auxin during the mobilization of reserves and the development of plant embryos of jatoba (Hymenaea courbaril var. Stilbocarpa)
Grantee:	Aline Dias Brandão
Support Opportunities:	Scholarships in Brazil - Doctorate

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