Shamir Michal Full Professor

(1) Revealing the enzymatic process of active anthocyanin degradation
(2) Phenylpropanoid pathways affecting pigmentation and fragrance
(3) Applied research for improving pigmentation in ornamentals
(4) Effect of colored nets on the yield and quality of ornamental crops

Revealing the enzymatic process of active anthocyanin degradation

How are anthocyanins degraded in plants? What role does the pigment catabolism process play in the final determination of pigment concentration in flower foliage or fruit? These are two of the major current research questions of my group. In contrast to the detailed knowledge available on the biosynthesis of anthocyanins, very little is known about the stability and degradation of these pigments in plant tissue.

Our model system is Brunfelsia calycina flowers, which change color from dark purple to white within two days. We are characterizing in planta anthocyanin turnover and degradation. In particular, we have identified, for the first time, an anthocyanin degrading enzyme, responsible for flower color change. We are also characterizing the metabolomics and genomic changes occurring during the change of color in Brunfelsia flowers, accompanied by production of flower fragrant compounds.

Phenylpropanoid pathways affecting pigmentation and fragrance

We expanded our studies to interactions between anthocyanin and other phenyproanoid pathways, especially the benzenoid pathway responsible for production of fragrant compounds. Parallel to the degradation of anthocyanins, Brunfelsia flowers produce fragrant volatiles, making this flower an interesting model for studying the relationship between pigment and fragrance production pathways. We use a number of profiling approaches to examine anthocyanin composition, volatile compound production, metabolite accumulation, and transcriptional and protein changes occurring during and after flower opening.
A second approach for studying the link between the different phenylpropanoid pathways (including anthocyanin pigments and benzenoid folatiles) is overexpressing the production of aromatic amino acids and in particular phenylalanine. The tool that we use for overproducing phenylalanine, the source for production of both anthocyanins and benzenoids is a feedback insensitive enzyme along the shikimate pathway. We are currently studying the metabolic and genomic effect of increased phenylalanine concentrations in genetically engineered petunia, lisianthus and in a grape cell culture.

Applied research for improving pigmentation in ornamentals

In order to improve and increase the quality of horticultural products, we develop solutions for optimization of anthocyanin pigmentation, based on characterization of the best conditions for anthocyanin accumulation in ornamental crops. This research includes testing best quality greenhouse covers for maximum pigmentation, and treatments for increasing pigmentation in plants, including hormonal treatments for inducing biosynthesis and treatments for stabilizing the anthocyanins in the plant tissues.

Effect of colored nets on the yield and quality of ornamental crops

The technology of plant production under colored shade nets, instead of the black neutral net,  is based on fact that plants are extremely sensitive to light quality, and that the adaptation to light changes occurs via a wide and complex network of photoreceptors. We were the first to use photoselective nets to improve the quality and yield of crops and are continuing experiments using this technology. We showed that by changing the direction and quality of the light by filtering sunlight through photoselective nets, we can improve the quality of ornamentals and increase their yield. At present we are focusing our work on testing the effect of shading mother-plants with photoselective nets, on the rooting of their cuttings.