Closely-related Xanthomonas citri subsp. citri isolates trigger distinct histological and transcriptional responses in Citrus limon

INGRID GEORGINA ORCE; MARIO DEBES; LORENA SENDÍN; ANA LUQUE; MARTA ARIAS, ; ADRIÁN VOJNOV; MARÍA MARANO; ATILIO CASTAGNARO; MARÍA PAULA FILIPPONE

SCIENTIA AGRICOLA

UNIV SAO PAOLO

Lugar: Piracicaba; Año: 2016 vol. 7 p. 489 - 565

0103-9016

Citrus canker, caused by Xanthomonas citri subsp. citri (Xcc), has an importanteconomic impact on the citrus industry. Extensive information is available about the disease but,nevertheless, the study of plant-pathogen interactions could provide new information in the understandingof citrus canker disease. A new isolate has been identified, Xcc AT, which has a highgenetic similarity (> 90 %) to the virulent Xcc T strain based on genetic clustering analyses ofthe rep-PCR fingerprinting patterns, but it does not produce cankerous lesions in Citrus limon. Inthis study, we compared C. limon responses to Xcc AT and to the virulent Xcc T strain at both histologicaland transcriptional levels. Histologically, leaves inoculated with Xcc AT exhibited neithera typical disordering of the spongy mesophyll, nor a swelling of epidermis. A particular content(undetermined) was also found in mesophyll cells near the stomata, together with increasedstarch accumulation. The transcriptomic profiles were compared by cDNA-AFLP technique. A totalof 121 fragments derived from transcript (TDF) were either specifically induced or repressedby the isolates, and 62 were sequenced. Analysis of global expression identified different classesof genes known to be involved in plant-pathogen interactions. This study constitutes the first approachof the specific interaction between the avirulent Xcc AT isolate and C. limon.Keywords: cDNA-AFLP, gene expression, canker, plant defense, microscopy