Browsing by Author "Kotze, Liske Marinate"

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    An investigation into the effects of smoke-water and GR24 on the growth of nicotiana benthamiana seedlings
    (Stellenbosch : University of Stellenbosch, 2010-12) Kotze, Liske Marinate; Hills, Paul N.; Kossmann, J. M.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics. Institute for Plant Biotechnology (IPB)
    ENGLISH ABSTRACT: Novel plant growth regulating substances (PGRs) are emerging as a useful tool to investigate important growth traits in plants. This study reports on growth promotion pathways leading to enhanced biomass accumulation in two PGRs sharing a common α, β-unsaturated furanone moiety. Growth promotion by GR24, a synthetic strigolactone, and an aqueous smoke solution (including the active compound, KAR1) in physiologically normal seedlings was characterized by enhanced biomass accumulation and higher seedling vigour. Root architecture (lateral root number and root length) and shoot size (fresh and dry shoot weight and leaf area) were also dramatically improved following GR24 and smoke/KAR1 treatment. Despite these apparent similarities, parallel transcript and phytohormone profiling identified only a limited number of overlapping entities. Four common up-regulated and nineteen down-regulated mRNA transcripts were identified; whilst amongst the phytohormones that were analyzed, only ABA and JA levels were commonly increased between the treatments. This suggests that, whilst the phenotypic end response(s) was similar, it was attained via distinct pathways. The limited number of co-expressed transcripts between these treatments, as well as repressed biomass accumulation when combining GR24 and aqueous smoke in a single treatment suggests, however, that a certain degree of cross-talk in either signal perception/transduction and/or biomass regulation could not be ruled out. In light of the structural similarity between the strigolactone and KAR1 molecules and the degree of redundancy between these treatments, it is possible that these two molecules might share a common receptor/perception pathway. Two silencing vectors were constructed, specifically aimed at silencing Nicotiana benthamiana genes MAX4 and MAX2 which are known to function in the strigolactone biosynthesis pathway and signal transduction pathway, respectively. Transgenes designed to express single- or double-stranded-self- complementary hairpin RNA have a post translational gene silencing effect. The pHELLSGATE2 plasmid a binary vector that incorporates GATEWAY cloning technology which makes use of λ-phage-based site specific recombination, rather than restriction endonucleases and ligation, was used to construct these gene silencing vectors. These constructs can in future be used to produce Nicotiana plants with impaired strigolactone production and perception abilities and may provide evidence as to whether the signaling cascade of KAR1 and strigolactone share a degree of crosstalk.