Genes involved in biosynthesis and signalisation of ethylene in Brassica oleracea and Arabidopsis thaliana: identification and genome comparative mapping of specific gene homologues.

The study reported was aimed at the identification and determination of the chromosomal organisation of genes involved in the ethylene biosynthesis and signalling pathways in Brassica oleracea, on the basis of the Arabidopsis thaliana DNA probes and in silico genome analysis. Because of its polyploidal origin, the B. oleracea genome is characterised by extensive gene redundancy. Therefore, an important aspect of gene expression in B. oleracea response to environmental stimuli is to identify the specific gene copy involved. This aspect should also be taken into consideration while studying the genetic basis of biosynthesis and signal transduction in relation to basic phytohormones. Our present work concerns the identification of homologue genes involved in ethylene biosynthesis such as SAM, ACS and ACO, as well as those involved in the ethylene signalling pathway, mainly ETR1, CTR1, MKK4, MKK5, EIN2, EIN3, EREBP, ERF5 and ERF7 on the basis of the restriction fragment length polymorphism (RFLP) and PCR mapping. In the case of ACC synthases, (ACSs) the in silico analysis of gene variants in the genome of A. thaliana was followed by the identification of homologues to ACS2, ACS6 and ACS7 in the B. oleracea database. In total, 22 loci with sequence homology to the genes under analysis were included in the existing B. oleracea RFLP chromosomal map. Based on the stress responsiveness of most of the A. thaliana genes analysed in this study, we performed initial functional analysis of some gene homologues mapped. With the use of the RT-PCR approach the conservation of differential transcriptional induction of ACS homologues in the B. oleracea and A. thaliana was demonstrated during ozone stress.