PR gene families of citrus: their organ specific-biotic and abiotic inducible expression profiles based on ESTs approach

Abstract

In silico expression profiles, of the discovered 3,103 citrus ESTs putatively encoding for PR protein families (PR-1 to PR-17), were evaluated using the Brazil citrus genome EST CitEST/database. Hierarchical clustering was displayed to identify similarities in expression patterns among citrus PR-like gene families (PRlgf) in 33 selected cDNA libraries. In this way, PRlgf preferentially expressed by organ and citrus species, and library conditions were highlighted. Changes in expression profiles of clusters for each of the 17 PRlgf expressed in organs infected by pathogens or drought-stressed citrus species were displayed for relative suppression or induction gene expression in relation to the counterpart control. Overall, few PRlgf showed expression 2-fold higher in pathogen-infected than in uninfected organs, even though the differential expression profiles displayed have been quite diverse among studied species and organs. Furthermore, an insight into some contigs from four PRlgf pointed out putative members of multigene families. They appear to be evolutionarily conserved within citrus species and/or organ-or stress-specifically expressed. Our results represent a starting point regarding the extent of expression pattern differences underlying PRlgf expression and reveal genes that may prove to be useful in studies regarding biotechnological approaches or citrus resistance markers.

Citrus genomics

“…Genes related to reorganization of cell walls, ion transport and water stress were up-regulated in plants with CVC, supporting functions to allow plant survival. Up-regulated defense response genes associated with oxidative stress (Peroni et al 2007) and PR proteins (PR 7, PR 10) (Campos et al 2007) were found only in symptomatic plants, suggesting that although the defense machinery was activated, it was insufficient to block the disease completely. The processes of pathogen recognition may be triggered later, when the bacteria are already established within the plant, a common characteristic in susceptible responses to pathogens.…”

Germin and Germin-like Proteins: Evolution, Structure, and Function

“…These proteins generate hydrogen peroxide that can be toxic to different types of attackers or could directly or indirectly stimulate plant-defense responses (Quan et al, 2007). PR-15 and PR-16 are known to be widely expressed in a range of Citrus tissues (Campos et al, 2007). In an interesting, though relatively small scale evolutionary study, the genes encoding 13 classes of these PR proteins were examined for positive selection using maximum-likelihood (ML) models of codon substitution (Scherer et al, 2005).…”

The effect of salt stress on Arabidopsis thaliana and Phelipanche ramosa interaction

“…We also examined the expression of genes involved in biotic stress including PR1 and PDF1.2 . PR proteins are defined as proteins encoded by host plants that are induced in pathological or related situations and represent major quantitative alterations in soluble protein during the defence response (Campos et al ., ). PR1 gene expression is used as a molecular marker for SAR.…”

“…In plants, glutathione S‐transferase (GST) gene expression is related to detoxification of ROS and induced by phytohormones and various stress factors (Table ) (Chen et al ., ). Other factors that are implicated in salt stress as well as biotic stress are the pathogenesis‐related ‐(PR) proteins (Campos et al ., ). Hence, transcriptional activation of PR genes plays an important role in the expression of resistance (Jalali et al ., ).…”