Screening and evaluation of promoters and target genes aiming to citrus huanglongbing (greening) resistance

• Grant number: 08/01208-6
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Effective date (Start): June 01, 2008
• Effective date (End): July 31, 2008
• Field of knowledge: Biological Sciences - Genetics - Plant Genetics
• Principal Investigator: Marcos Antonio Machado
• Grantee: Natalia Cristina Verza Ferreira
• Host Institution: Instituto Agronômico (IAC). Agência Paulista de Tecnologia dos Agronegócios (APTA). Secretaria de Agricultura e Abastecimento (São Paulo - Estado). Campinas , SP, Brazil
• Associated research grant: 05/00718-2 - Studies on the bacterium Candidatus Liberibacter spp., causal agent of citrus huanglongbing (ex-greening): diagnosis, biology and management, AP.TEM

Abstract

The citrus industry is one of the most important activities of the agribusiness in Brazil,where the state of São Paulo is the main citrus producer and exporter of Frozen Concentrated Orange Juice (FCOJ). In Brazil, the low yield (around 2 boxes/tree/year) is highly associated to the incidence of pests and diseases (resulting in a substantial influence over the production costs), the production in non-irrigated areas, and the narrow genetic basis that has been used (i.e., only a few varieties grown in most of the orchards).In the past 20 years, many economically important diseases and pests have occurred in Brazil, which includes citrus variegated chlorosis (CVC), leprosis, black spot, Alternariabrown spot, sudden death, citrus fruit borer, citrus leaf miner (CLM), scales, etc. Until recently, there has not been reported in the Western Hemisphere the occurrence of the Huanglongbing (ex-greening), an extremely aggressive and damaging citrus disease wherever it occurs in the world. However, in 2004, the causal agent of the disease, the bacterium Candidatus Liberibacter spp. was for the first time found in the state of Sao Paulo in citrus plants that resembled its typical symptoms. Huanglongbing is one of the most destructive and severe diseases of citrus and causes damages in the plant development (chlorosis, leaf drop, and reduction of growth and roots) and fruit (misshapen, seed abortion, drop, and growth reduction). The causal agent is a phloem-limited bacterium, which has not been isolated so far, and is transmitted by the Asian citrus psyllid (Diaphorina citri), an insect easily found in Brazil. The existence of resistant plants may be an effective way to contend the disease. The objective of this project is the identification and the cloning of genes involved in the resistance to HBL as well as tissue-specific promoters using the information available in the CitEST, the Expressed Citrus Genome Project database. Tissue-specific transcripts will be identified using in silico approaches, and their expression pattern confirmed by RT-PCR experiments. Genes potentially related to HBL resistance will be identified and cloned in expression cassettes, likewise promoters of specific expression. Specific promoters acting at the phloem must be identified, and it should be used for obtaining transgenic plants resistant to HBL disease. (AU)