לוח שנה משולב

Epicuticular waxes coat the aerial parts of land plants almost ubiquitously. These waxes consist mainly of very long chain fatty acids and their derivatives, though epicuticular wax exact composition may vary greatly between plant species. Despite their wide distribution and decades of extensive study, the role of cuticular lipids in sustaining plant fitness is far from being understood. The main goal of my PhD research has been therefore to answer this fundamental question. To this end, I identified 16 different cuticular lipid related genes based on their enriched expression in the leaf epidermis and slight drought induction and generated knock out mutations in these genes using the CRISPR Cas9 system. Of these 16 mutants, nine displayed a cuticular lipid related phenotype and five were selected for further analysis. The mutated plants had a reduced wax load, or were completely lacking certain wax components altogether. This led to drastic shifts in wax crystal structure and to elevated cuticular water loss, although under non stressed conditions plants with an altered wax composition did not have elevated transpiration. In contrabst, once exposed to drought plants lacking alkanes were not able to strongly reduce their transpiration, leading to leaf death and impaired recovery upon resuscitation. When interactions of snails and insects with this mutant populations were examined, I found that these interactions were best divided based on their type – leaf chewing, phloem feeding or non-feeding interactions. Here I found that fatty alcohols were correlated with reduction in caterpillar weight gain, while cutin but not wax composition affected phloem feeders. Non feeding interactions examined in tobacco white fly showed an effect of wax crystal structure rather than chemical composition. Finally, to examine the effects of epicuticular wax under natural conditions two field plots were planted with these mutants and monitored during several months. I found, that similar to the results of the drought trials, under non-competitive conditions epicuticular wax had little effect on plant fitness. however, when plants were under severe competition with foreign plants, all wax components contributed greatly to fitness. in these plots, similar to the caterpillar assays, caterpillars from a wider range of species preferred the fatty alcohol devoid far mutants. These were also preferred by web weavers, and especially spiders. From this diverse range of settings and interactors I concluded that under optimal conditions, epicuticular wax has little effect on plant fitness. however, once conditions are stressful epicuticular wax contributes greatly whether these conditions be drought, competing vegetation or insect herbivores eating the plants’ leaves. That being said, not all wax components contribute equally to every process. Alkanes are essential for drought recovery while fatty alcohols reduce insect herbivory.

Maintaining average activity level within a set-point range constitutes a fundamental property of central neural circuits. Accumulated evidence suggests that firing rate distributions and their means represent physiological variables regulated by homeostatic systems. Utilizing basic concepts of control theory, we developed a theoretical and experimental framework for identifying the core members of homeostatic machinery. I will describe an integrative approach to study the relationships between ongoing spiking activity of individual neurons and neuronal populations in local microcircuits, synaptic transmission and plasticity, sleep and memory functions. I will show our new data on a state-dependent regulation of firing rate set-points, their dysregulation at the presymptomatic stage of Alzheimer’s disease, and the role of mitochondria in these processes.