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Koltai H.,Institute of Plant science
Trends in Plant Science | Year: 2014

Strigolactones, previously identified as active stimuli of seed germination in parasitic plants, are now recognized as a new group of plant hormones that are active in both shoots and roots. Here, we review recent insights into the concepts of strigolactones-signal transduction and their mode of action. Although strigolactones are sensed via a cell-specific reception system, at least some aspects of their activity are conducted in a non-cell-autonomous fashion. Strigolactones also affect trafficking and plasma-membrane localization of the auxin transporter PIN, thereby regulating auxin flux. We present a model for strigolactone-signal transduction that might also explain the integration of strigolactones into other hormone-signaling pathways via the regulation of PIN auxin transporters. © 2014 Elsevier Ltd.

Ashkenazy H.,Tel Aviv University | Penn O.,Tel Aviv University | Doron-Faigenboim A.,Institute of Plant science | Cohen O.,Tel Aviv University | And 3 more authors.
Nucleic Acids Research | Year: 2012

Ancestral sequence reconstruction is essential to a variety of evolutionary studies. Here, we present the FastML web server, a user-friendly tool for the reconstruction of ancestral sequences. FastML implements various novel features that differentiate it from existing tools: (i) FastML uses an indel-coding method, in which each gap, possibly spanning multiples sites, is coded as binary data. FastML then reconstructs ancestral indel states assuming a continuous time Markov process. FastML provides the most likely ancestral sequences, integrating both indels and characters; (ii) FastML accounts for uncertainty in ancestral states: it provides not only the posterior probabilities for each character and indel at each sequence position, but also a sample of ancestral sequences from this posterior distribution, and a list of the k-most likely ancestral sequences; (iii) FastML implements a large array of evolutionary models, which makes it generic and applicable for nucleotide, protein and codon sequences; and (iv) a graphical representation of the results is provided, including, for example, a graphical logo of the inferred ancestral sequences. The utility of FastML is demonstrated by reconstructing ancestral sequences of the Env protein from various HIV-1 subtypes. FastML is freely available for all academic users and is available online at http://fastml.tau.ac.il/. © 2012 The Author(s).

Bar-Ziv A.,Institute of Plant science
Plant signaling & behavior | Year: 2012

The V2 protein of Tomato yellow leaf curl geminivirus (TYLCV) is an RNA-silencing suppressor that counteracts the innate immune response of the host plant. However, this anti-host defense function of V2 may include targeting of other defensive mechanisms of the plant. Specifically, we show that V2 recognizes and directly binds the tomato CYP1 protein, a member of the family of papain-like cysteine proteases which are involved in plant defense against diverse pathogens. This binding occurred both in vitro and in vivo, within living plant cells. The V2 binding site within mCYP1 was identified in the direct proximity to the papain-like cysteine protease active site.

Kamenetsky R.,Institute of Plant science
Acta Horticulturae | Year: 2011

Ornamental geophytes belong to numerous botanical taxa and show remarkable diversity with regard to morphology, developmental biology, genetic control and response to the environment. Flower development of geophytes is greatly influenced both by the genetics of the individual plant and by environmental factors; their interactions affect a series of molecular and biochemical processes leading to the transition of the plant from vegetative to reproductive development. While the morphological and physiological aspects of florogenesis have been studied in several bulbous species, there is still only limited information on the genetic control of meristem transition, formation of inflorescence, individual flowers, and flower parts. Elucidating the genetic control of florogenesis in geophytes is important, not only for better understanding of their developmental biology, but also because of their agronomic and economic importance. Molecular characterization of genes involved in flower morphology could help to develop novel floral architecture in flower bulbs by classical breeding or by genetic manipulations. Until now, most genetic studies have been performed on commercially important crops. However, a model bulbous species has to stand several specific criteria: a short juvenile period, easy pollination and seed germination, well studied morphological and physiological aspects, an established transformation system. Recent results, prospects and future investigations of physiological, biochemical and molecular mechanisms of florogenesis in ornamental geophytes are discussed.

Mahesh A.,Institute of Plant science | Jeyachandran R.,St. Josephs College
Plant Biosystems | Year: 2011

Hairy roots were efficiently induced from leaf and petiole explants of Taraxacum officinale after infection with the Agrobacterium rhizogenes strains A4 and ATCC 15834. The highest frequency of hairy root initiation was observed after transformation of leaf explants with the A4 strain. Hairy roots developed from leaf tissue produced more biomass than nontransformed roots. A quantitative study of sesquiterpene lactones showed that A. rhizogenes induced root cultures accumulated higher levels of these compounds than non-transformed and wild plant roots. The present results demonstrate that T. officinale hairy root culture is a valuable alternative approach for the production of sesquiterpene lactones. © 2011 Società Botanica Italiana.

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