Transcriptional and Morphological Study for the Role of Ethylene in the Response to Inclination in Pine

Loss of verticality in conifers affects the normal wood development by inducing changes and chemical modifications in tree stems. Ethylene influences the response during this abnormal wood-forming process, and expression pattern of genes involved in the ethylene biosynthesis pathway due to inclination in gymnosperm has been reported in adult trees. Young seedlings of radiata pine were inclined to reveal the expression pattern of these genes by the quantitative real-time PCR (qRT-PCR) technique. Seedlings were exposed to inclination and harvested after 2,5 and 10 h (early response), and after 24 h (late response). Sampling includes transverse cuts at three height of the whole stem of inclined seedlings. Our data revealed that genes encoding for 1-aminocyclopropane-1-carbxylate oxidase (ACO) and 1-aminocyclopropane-1-carboxylate synthase (ACS) were differentially expressed during the time of leaning, and, interestingly, at the basal portion of radiata pine stems. Inclined plants increase cell wall thickness after 15d. Also, more rounded shape of xylem cells, and accumulation of lignin were observed. Application of ethephon accelerated significantly these changes which could be observed after 5 d of inclination. Transcriptional analyses showed an up-regulation of genes encoding phenylalanine ammonia lyase and cinnamyl alcohol dehydrogenase after inclination and their possible ethylene signal dependence.

Research supported by Fondecyt 1120635.