Osmotin induces cold protection in olive trees by affecting programmed cell death and cytoskeleton organization

Abstract

Osmotin is a pathogenesis-related protein exhibiting cryoprotective functions. Our aim was to understand whether it is involved in the cold acclimation of the olive tree (Olea europaea L.), a frost-sensitive species lacking dormancy. We exposed olive trees expressing tobacco osmotin gene under the 35S promoter (35S:osm) [in the same manner as wild type (wt) plants] to cold shocks in the presence/absence of cold acclimation, and monitored changes in programmed cell death (PCD), cytoskeleton, and calcium ([Ca2+]c) signalling. In the wt, osmotin was immunolocalized only in cold-acclimated plants, and in the tissues showing PCD. In the 35S:osm clones, the protein was detected also in the non-acclimated plants, and always in the tissues exhibiting PCD. In the non-acclimated wt protoplasts exposed to cold shock, a transient decrease in phallotoxin signal suggests a temporary disassembly of F-actin, a transient increase occurred instead in 35S:osm protoplasts exposed to the same shock. Transient increases in [Ca2+]c were observed only in the wt protoplasts. However, when F-actin was depolymerized by cytochalasin or latrunculin, and microtubules by colchicine, increase in [Ca2+]c also occurred in the 35S:osm protoplasts. Successive cold shocks caused transient rises in [Ca2+]c and transient decreases in the phallotoxin signal in wt protoplasts. No change occurred in [Ca2+]c occurred in the 35S:osm protoplasts. The phallotoxin signal transiently increased at the first shock, but did not change after the subsequent shocks, and an overall signal reduction occurred with shock repetition. Following acclimation, no cold shock-induced change in [Ca2+]c levels and F-actin signal occurred either in wt or 35S:osm protoplasts. The results show that osmotin is positively involved in the acclimation-related PCD, in blocking the cold-induced calcium signalling, and in affecting cytoskeleton in response to cold stimuli.

The activities of catalase and ascorbate peroxidase in olive (Olea europaea L. cv. Gemlik) under low temperature stress

“…In some cases higher quality oil is sought in areas with cold autumns where the post-ripening period is longer (Palliotti and Bongi, 1996). However, olive tree lives in warm temperatures showing low tolerance to frost (D'Angeli and Altamura, 2007). These trees can not survive below -12 (Gómez-del-Campo and Barranco, 2005) and are damaged by frost below -7 , reducing productivity (Palliotti and Bongi, 1996).…”

Studies on genetic transformation of olive (Olea europaea L.) somatic embryos: I. Evaluation of different aminoglycoside antibiotics for nptII selection; II. Transient transformation via particle bombardment

“…The Agrobacterium-mediated transformation of cultivar 'Canino' with rolABC genes from A. rhizogenes to modify vegetative growth and an osmotin gene for increasing resistance to biotic stress has been reported (Rugini et al 2000;Rugini and Gutiérrez-Pesce 2006;D'Angeli and Altamura 2007). Mencuccini et al (1999) also used A. tumefaciens to introduce rolABC genes in cv.…”

Unsaturated Lipids Change in Olive Tree Drupe and Seed during Fruit Development and in Response to Cold-Stress and Acclimation

“…In non-cold-acclimated olive tree plants, the cold stress response is characterized by changes intervening at different cell and tissue levels in leaves and twigs [6,12]. The cell membranes are the primary site of cold-induced injury, but, when cold-acclimation is present, it causes the activation of mechanisms protecting membrane fluidity by ensuring the activity of the fluidity-related enzymes [13].…”

“…The cell membranes are the primary site of cold-induced injury, but, when cold-acclimation is present, it causes the activation of mechanisms protecting membrane fluidity by ensuring the activity of the fluidity-related enzymes [13]. Among these mechanisms there are changes in lipid composition and transient increases in cytosolic calcium levels, both involved in the signal transduction leading to the activation of acclimation-related genes [12,13]. However, how plants decode low temperature message into changes in transcription and lipid composition still remains a widely unresolved question [14], and in woody perennials, in particular.…”