Induction of Pinus sylvestris PsACRE, a homology of Avr9/Cf-9 rapidly elicited defense-related gene following infection with root rot fungus Heterobasidion annosum

Abstract

A novel defense-related gene code named PsACRE, an Avr9/ Cf- 9 rapidly elicited ( ACRE) gene homology was isolated from the conifer tree Scots pine ( Pinus sylvestris) following infection with the root rot pathogen— Heterobasidion annosum. This is the first report of such genes to be characterized in conifer species. The full length PsACRE gene sequence from the Scots pine was obtained using the rapid amplification of cDNA ends (RACE) method with the aid of gene-specific primers. The transcript of ∼1.1 kb encodes a peptide of 207 amino acids with a 5′-untranslated region of about 210 bp long and a 3′-untranslated region of about 224 bp long. The peptide encoded by the PsACRE share high homology to a gene from Nicotiana tabacum described to encode ACRE protein 146. Amino acid analyses confirmed that the PsACRE gene belongs to leucine rich repeat (LRR) gene superfamilies. Southern gel blot analysis of genomic DNA following digestion with three restriction enzymes ( BamHI, EcoRI, HindIII) indicated that several copies of the gene are present in Scots pine genome. RNA gel blot analyses showed that the PsACRE gene was highly expressed in root and stem regions compared to needle tissues. Further, Northern analyses confirmed that the PsACRE gene expression is elevated in Scots pine roots upon infection with H. annosum. The potential significance of the PsACRE gene in host–parasite interaction in conifer pathosystem is discussed.