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Mailing Address:
The Robert H. Smith Institute of
Plant Sciences and Genetics
in Agriculture
POB 12, Rehovot 76100, Israel

Administrator: Neomi Maimon 
Tel: 972-8-948-9251,
Fax: 972-8-948-9899,
E-mail: neomim@savion.huji.ac.il

Director: Prof. David Weiss
Tel: 972-8-948-9436
Fax: 972-8-948-9899
E-mail: david.weiss@mail.huji.ac.il

 

Publications

2020
Tsamir-Rimon, M. ; Ben-Dor, S. ; Feldmesser, E. ; Openheimer- Shaanan, Y. ; David-Schwartz, R. ; Samach, A. ; Klein, T. Rapid starch degradation in the wood of olive trees under heat and drought is permitted by three stress-specific beta amylases. New Phytologist 2020, n/a. Publisher's VersionAbstract
Abstract Carbon reserve use is a major drought response in trees, enabling tree survival in conditions prohibiting photosynthesis. However, regulation of starch metabolism under drought at the whole-tree scale is still poorly understood. To this end, we combined measurements of nonstructural carbohydrates (NSC), tree physiology and gene expression. The experiment was conducted outside on olive trees in pots under 90 days of seasonal spring to summer warming. Half of the trees were also subjected to limited water conditions for 28 days. Photosynthesis decreased in dehydrating trees from 19 to 0.5 µmol m-2 s-1 during the drought period. Starch degradation and mannitol production were a major drought response, with mannitol increasing to 71% and 41% out of total NSC in shoots and roots, respectively. We identified the gene family members potentially relevant either to long-term or stress-induced carbon storage. Partitioning of expression patterns among β amylase and starch synthase family members was observed, with three β amylases possibly facilitating the rapid starch degradation under heat and drought. Our results suggest a group of stress-related, starch metabolism genes, correlated with NSC fluctuations during drought and recovery. The daily starch metabolism gene expression was different from the stress-mode starch metabolism pattern, where some genes are uniquely expressed during the stress-mode response.
2018
Haberman, A. ; Flaishman, M. A. ; Samach, A. Do gibberellins inhibit flowering of transgenic pears with silenced TFL1-encoding genes?. In Acta Horticulturae; Acta Horticulturae; International Society for Horticultural Science (ISHS), Leuven, Belgium, 2018; pp. 43 - 46. Publisher's Version
Jover-Gil, S. ; Beeri, A. ; Fresnillo, P. ; Samach, A. ; Candela, H. Complete genome sequence of a novel virus, classifiable within the Potyviridae family, which infects passion fruit (Passiflora edulis). Arch Virol 2018, 163, 3191-3194.Abstract
We report the complete nucleotide sequence of a new member of the Potyviridae family isolated from passion fruit plants grown in Israel, called Passiflora edulis symptomless virus (PeSV). The PeSV genome is 9,928 nucleotides long and encodes a 3,173 amino acids polyprotein that is predicted to be proteolytically cleaved into 10 mature peptides. Our phylogenetic analysis shows that PeSV represents a new species, and is most closely related to rose yellow mosaic virus (RoYMV). According to currently accepted criteria for genus demarcation, both viruses should be assigned as representative isolates of new species in the recently approved genus, Roymovirus, in the Potyviridae family.
2017
Haberman, A. ; Bakhshian, O. ; Cerezo-Medina, S. ; Paltiel, J. ; Adler, C. ; Ben-Ari, G. ; Mercado, J. A. ; Pliego-Alfaro, F. ; Lavee, S. ; Samach, A. A possible role for flowering locus T-encoding genes in interpreting environmental and internal cues affecting olive (Olea europaea L.) flower induction. Plant, Cell & Environment 2017, 40, 1263-1280. Publisher's VersionAbstract
Abstract Olive (Olea europaea L.) inflorescences, formed in lateral buds, flower in spring. However, there is some debate regarding time of flower induction and inflorescence initiation. Olive juvenility and seasonality of flowering were altered by overexpressing genes encoding flowering locus T (FT). OeFT1 and OeFT2 caused early flowering under short days when expressed in Arabidopsis. Expression of OeFT1/2 in olive leaves and OeFT2 in buds increased in winter, while initiation of inflorescences occurred i n late winter. Trees exposed to an artificial warm winter expressed low levels of OeFT1/2 in leaves and did not flower. Olive flower induction thus seems to be mediated by an increase in FT levels in response to cold winters. Olive flowering is dependent on additional internal factors. It was severely reduced in trees that carried a heavy fruit load the previous season (harvested in November) and in trees without fruit to which cold temperatures were artificially applied in summer. Expression analysis suggested that these internal factors work either by reducing the increase in OeFT1/2 expression or through putative flowering repressors such as TFL1. With expected warmer winters, future consumption of olive oil, as part of a healthy Mediterranean diet, should benefit from better understanding these factors.
2016
Tal, Y. ; Anavi, S. ; Reisman, M. ; Samach, A. ; Tirosh, O. ; Troen, A. M. The neuroprotective properties of a novel variety of passion fruit. Journal of Functional Foods 2016, 23, 359 - 369. Publisher's VersionAbstract
Passion fruit is a commercially important crop. The neuroprotective activity of fruit extracts from two hybrid lines of antioxidant ester thiol-rich Passiflora edulis Sims, the commercial “Passion Dream” and novel cultivar 428 (“Dena”) line were studied. Crude extracts from line 428 displayed the strongest dose-dependent neuroprotective activity, preventing glutamate induced cell-death, mitochondrial depolarization and glutathione depletion, when added to the medium of cultured HT4 neurons (p < 0.05). Supplementing diet of mice with the 428 fruit-extract improved survival of dopaminergic neurons by 60% in mice injected with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MTPT) compared to control-fed MPTP-injected mice (p < 0.05). The neuroprotection conferred by passion fruit extracts in vivo and in vitro shows promise for further research into their bioactive potential for medical exploitation.
Haberman, A. ; Ackerman, M. ; Crane, O. ; Kelner, J. - J. ; Costes, E. ; Samach, A. Different flowering response to various fruit loads in apple cultivars correlates with degree of transcript reaccumulation of a TFL1-encoding gene. Plant J 2016, 87, 161-73.Abstract
In many perennial fruit trees, flowering in the year following a year with heavy fruit load can be quite limited. This biennial cycle of fruiting, termed alternate bearing, was described 170 years ago in apple (Malus domestica). Apple inflorescences are mainly found on short branches (spurs). Bourse shoots (BS) develop from the leaf axils of the spur. BS apices may terminate ~100 days after flowering, with formation of next year's inflorescences. We sought to determine how developing fruit on the spur prevents the adjacent BS apex from forming an inflorescence. The presence of adjacent fruit correlated with reaccumulation of transcript encoding a potential flowering inhibitor, MdTFL1-2, in BS apices prior to inflorescence initiation. BS apices without adjacent fruit that did not flower due to late fruitlet removal, neighbouring fruit on the tree, or leaf removal, also reaccumulated the MdTFL1-2 transcript. Fruit load and gibberellin (GA) application had similar effects on the expression of MdTFL1-2 and genes involved in GA biosynthesis and metabolism. Some apple cultivars are less prone to alternate bearing. We show that the response of a BS apex to different numbers of adjacent fruit differs among cultivars in both MdTFL1-2 accumulation and return flowering. These results provide a working model for the further study of alternate bearing, and help clarify the need for cultivar-specific approaches to reach stable fruit production.