Comparative analysis of differentially expressed sequence tags of sweet orange and mandarin infected with Xylella fastidiosa

Abstract

The Citrus ESTs Sequencing Project (CitEST) conducted at Centro APTA Citros Sylvio Moreira/IAC has identified and catalogued ESTs representing a set of citrus genes expressed under relevant stress responses, including diseases such as citrus variegated chlorosis (CVC), caused by Xylella fastidiosa. All sweet orange (Citrus sinensis L. Osb.) varieties are susceptible to X. fastidiosa. On the other hand, mandarins (C. reticulata Blanco) are considered tolerant or resistant to the disease, although the bacterium can be sporadically detected within the trees, but no disease symptoms or economic losses are observed. To study their genetic responses to the presence of X. fastidiosa, we have compared EST libraries of leaf tissue of sweet orange Pêra IAC (highly susceptible cultivar to X. fastidiosa) and mandarin 'Ponkan' (tolerant) artificially infected with the bacterium. Using an in silico differential display, 172 genes were found to be significantly differentially expressed in such conditions. Sweet orange presented an increase in expression of photosynthesis related genes that could reveal a strategy to counterbalance a possible lower photosynthetic activity resulting from early effects of the bacterial colonization in affected plants. On the other hand, mandarin showed an active multi-component defense response against the bacterium similar to the non-host resistance pattern.

Differential colonization patterns of Xylella fastidiosa infecting citrus genotypes

“…This bacterium is able to cause CVC in all commercial sweet orange (C. sinensis) varieties, but the majority of other citrus genotypes such as mandarins (C. reticulata), limes (C. aurantifolia), lemons (C. limon) and tangors (C. sinensis 9 C. reticulata) are resistant to CVC in field conditions (Laranjeira et al, 1998). However, under greenhouse conditions, this bacterium has been shown to briefly colonize mandarins and tangors de Souza et al, 2007). Genetic studies have been performed to assess the genes involved in the defence responses of these resistant genotypes compared to the susceptible sweet orange (de Souza et al, 2009;Gmitter et al, 2012;Rodrigues et al, 2013).…”

Xylella fastidiosa: an examination of a re‐emerging plant pathogen

“…These observations may partially explain why particular grapevine cultivars that fail to induce phenolics to high concentrations, such as ‘Chardonnay’ or ‘Crimson Seedless’, display PD symptoms much sooner than other cultivars (Wallis and Chen, ). The accumulation of phenolic compounds has also been reported as a response to X. fastidiosa in CVC‐resistant citrus (de Souza et al ., ). The induction of genes involved in phenylpropanoid and flavonoid biosynthesis occurs as quickly as 1 day after inoculation in ‘Ponkan’ mandarin ( Citrus reticulata Blanco), a CVC‐resistant citrus variety (Rodrigues et al ., ).…”

Citrus Variegated Chlorosis: an Overview of 30 Years of Research and Disease Management

“…Certainly, the mandatory change of citrus nursery system production in São Paulo state from the open-field system to a certified program under screenhouses in 2003, was one of the most important strategies to manage CVC (Carvalho 2003). The publication of the whole genome sequence of the CVC-causing X. fastidiosa strain 9a5c (Simpson et al 2000) encouraged scientists with diverse expertise to work with this pathogen, resulting in significant scientific progress in understanding bacterial biology (de Souza et al , 2004Moreira et al 2004), pathogenicity (Habermann et al 2003;Moreira et al 2004;de Souza et al 2005;Rodrigues et al 2013), and host resistance strategies (de Souza et al 2007a;Garcia et al 2012;Caserta et al 2017).…”