The effect of plant derived smoke on germination, extent of eosine dye penetration and amount of abscisic acid (ABA) in the seeds of two Karoo non-fire-prone species: Ruschia caroli and Drosanthemum speciosum, and two fynbos fire-prone species: R. macowanii and D. stokoei, of Mesembryanthemum were investigated. The seed coat characteristics of each species were also investigated. Pierce et al. (1995) found that smoke promotes seed germination in the Karoo species R. caroli (scarified) and D. speciosum, whereas smoke has no effect on the germination of R. macowanii and D. stokoei (fynboss species). Results presented in this investigation support those of Pierce et al. (1995). The extent of dye penetration in smoke treated seeds if D. speciosum was significantly greater then that in untreated seeds of this species. This was due to the breakdown of some barrier, apparently in the membrane between the endosperm and the seed coat, by smoke. Seed ABA levels were reduced by smoke treatment in all four species, however this reduction was more pronounced in the smoke responsive species. Seeds coat studies revealed that the least responsive species was the only one to be covered by a waxy cuticle. Seed dormancy was a feature of the species in which seed was improved by germination, whereas the seeds of the unresponsive species, R. macowanii and D. stokoei were non-dormant. Hence, smoke appears to act as a dormancy release cue, having no, or little effect, on the seed germination of non-dormant species. Results from this study indicate that the mechanism of smoke triggered dormancy release involves the chemical alteration of the membrane bounding the endosperm and the reduction in the ABA concentration in the species investigated.

SKD1 (suppressor of potassium transport growth defect) belongs to the AAA-ATPase family and is one of the class E VPS (vacuolar protein sorting) proteins. The ATPase activity-deficient form of SKD1 leads the perturbation of mechanism transport through endosomes and lysosomes, however, the molecular mechanism behind the action of SKD1 is poorly understood. In this study, it is identified that VPS4_YEAST (Saccharomyces cerevisiae) is the homology protein of mcSKD1 (Mesembryanthemum crystallinum SKD1) employing sequence profile analysis. The full-length mcSKD1 protein possesses MIT, AAA-ATPase, and NACHT domains of VPS4_YEAST. It is investigated that VPS4_YEAST (NACHT domain) interacts to BRO1_YEAST (HEAT repeat), BRO1_YEAST (HEAT repeat) to AIP1_YEAST (WD40 repeat), AIP1_YEAST (WD40 repeat) to ABP1_YEAST (ADF domain), ABP1_YEAST (ADF domain) to ARP2_YEAST (ACTIN domain), respectively, from yeast two-hybrid system via protein-protein interaction. These proteins employ the function of cytoskeleton structural proteins in cells. Hence, mcSKD1 protein may involve the mechanisms of potassium ion uptake and salt tolerance via the function of cytoskeleton structural proteins.