Identification of upregulated genes in laminarin-treated poplar (Populus alba × P. tremula var. glandulosa) suspension cells by suppression subtractive hybridization and cDNA microarray

Elicitors trigger defence responses in plant cells through signal transduction pathways, leading to accumulation of pathogenesis-related (PR) proteins and, eventually, pathogen resistance. To understand defence responses of hybrid poplar (Populus alba × P. tremula var. glandulosa), we isolated and characterized upregulated genes in poplar cells by laminarin-induced elicitation using suppression subtractive hybridization (SSH) and cDNA microarray approaches. A total of 1,269 clones in the SSH library were sequenced and a cDNA microarray, containing 265 unique subtracted clones, was fabricated. From the microarray results, 37 clones were found to be upregulated by laminarin treatment and their putative functions are discussed. Genes involved in signal transduction, transcriptional regulation, and phytohormone biosynthesis were upregulated. Other genes encoding PR proteins, peptidases, and an ABC transporter, as well as genes involved in lignification and protein synthesis and turnover, were also identified. Our results suggest that well-organized defence responses, from signal transduction to accumulation of PR proteins, are activated in poplar cells by laminarininduced elicitation and could contribute to resistance against pathogens.