Plant & Animal Genomes XVII Conference

January 10-14, 2009
Town & Country Convention Center
San Diego, CA

ESTs Of Roots Of Different Citrus Species And Differential Expression Of Genes Associated To Drought Tolerance

Ana Carla Silva-Pinhati¹ , Raquel Luciana Boscariol-Camargo¹ , Adriano Malosso¹ , Alessandra Alves de Souza¹ , Alexandre Morais do Amaral^1,2 , Eduardo Fermino Carlos¹ , Juliana Freitas-Astua^1,3 , Marco Aurelio Takita¹ , Maria Luisa N.P. Targon¹ , Marcos Antonio Machado¹

¹  Centro de Citricultura Sylvio Moreira, Instituto Agronomico de Campinas Cordeiropolis - SP - BRAZIKL

²  Embrapa Recursos Geneticos e Biotecnologia

³  Embrapa Mandioca e Fruticultura

Biotic and abiotic stresses in citrus species are the main challenges to the breeding programs and to maintain the productivity at field conditions. Among abiotic factors affecting citrus growth water stress represents an important factor around the world, especially in no irrigated citrus orchards. Rangpur lime (Citrus limonia Osb. cv Santa Barbara, tolerant to water stress), Swingle citrumelo (C. paradisi x Poncirus trifoliata, less tolerant to water stress), and trifoliate orange (P. trifoliata cv. Rubidoux, susceptible to water stress) are important rootstocks in Brazil and in other citrus growing areas around the world. Aiming to compare the response to water stress conditions both ESTs libraries and gene expressions were evaluated in these three rootstocks. Libraries of 19,356 ESTs were produced (6325 of Rangpur lime, 7182 of Swingle citrumelo, and 5849 of P. trifoliata), and statistically evaluated to compare the frequency of more expressed sequences, which were used to follow up their expression by RT-qPCR. Roots under induced water stress were used in the biological assays. Selected genes for expression studies included the transcription factor CBF-1, the gene of the enzyme P5CS, germin-like gene, aquaporin, and dehidrin. Analysis of Rangpur lime revealed that germin-like, dehidrin and aquaporin were expressed lately, suggesting no participation in the initial response to the water stress. On the other hand, different response was obtained with p5cs and cbf genes that were quickly activated in Rangpur lime and Swingle citrumelo. These data suggested that transcription factors and proline are involved in initial responses of resistance to drought and could be responsible for the differences involving stress tolerance among the genotypes.
Support: CNPq and FAPESP.