Functional analysis of citrus reticulata SAMT gene in the resistance of citrus phytopathogen through overexpression in Nicotiana tabacum

Abstract

Since 1962 the citrus industry has significantly contributed to the development of the Brazilian agribusiness, making it responsible for 53% of the world production of orange juice with an annual income of US$ 1,5 billion. However, the management challenges due to the occurrence of pests and diseases have high production cost for the producer. In the last year, the amount spent on the management of Citrus Variegated Chlorosis (CVC) was around US$ 100 million, adding up to commercial losses and the fruit reduction and hardening, these symptoms being caused by the bacterium Xylella fastidiosa, the causal agent of CVC. The sequencing of the bacterium genome and studies of gene expression in susceptible and resistant hosts open perspectives for selecting genes with potential for development of resistant varieties. Some of these genes are involved in signaling pathways that activate the plant defense. One of the genes induced in the resistant host in response to the infection by X. fastidiosa was the S-adenosyl-methionine: Salicylic Acid Carboxyl Methyltransferase (SAMT). This gene encodes an enzyme that catalyzes the conversion of salicylic acid (SA) in methylsalicylate (MeSa), and is also involved in the interaction between the SA and Jasmonic Acid (JA) pathways and may be a mediator among them. We propose with this project, the study of interactions and phenotypic variations that may be generated due to overexpression of SAMT gene in Nicotiana tabacum model plants infected with X. fastidiosa, in order to understand the role of SAMT gene in the activation of defense pathways activated by SA or JA. (AU)