The Physiology and Proteomics of Drought Tolerance in Maize: Early Stomatal Closure as a Cause of Lower Tolerance to Short-Term Dehydration?

Understanding the response of a crop to drought is the first step in the breeding of tolerant genotypes. In our study, two maize (Zea mays L.) genotypes with contrasting sensitivity to dehydration were subjected to moderate drought conditions. The subsequent analysis of their physiological parameters revealed a decreased stomatal conductance accompanied by a slighter decrease in the relative water content in the sensitive genotype. In contrast, the tolerant genotype maintained open stomata and active photosynthesis, even under dehydration conditions. Drought-induced changes in the leaf proteome were analyzed by two independent approaches, 2D gel electrophoresis and iTRAQ analysis, which provided compatible but only partially overlapping results. Drought caused the up-regulation of protective and stress-related proteins (mainly chaperones and dehydrins) in both genotypes. The differences in the levels of various detoxification proteins corresponded well with the observed changes in the activities of antioxidant enzymes. The number and levels of up-regulated protective proteins were generally lower in the sensitive genotype, implying a reduced level of proteosynthesis, which was also indicated by specific changes in the components of the translation machinery. Based on these results, we propose that the hypersensitive early stomatal closure in the sensitive genotype leads to the inhibition of photosynthesis and, subsequently, to a less efficient synthesis of the protective/detoxification proteins that are associated with drought tolerance

Comparing the latency and amplitude of auditory-evoked brainstem responses in full-term and premature neonates

Background: Auditory-evoked potentials are brain waves produced by presenting acoustic signals to the person. Auditory-evoked brainstem responses (AEBR) are a part of auditory evoked potentials seen in a time range less than 10 ms after the delivery of high intensity stimulation. Considering the effect of maturation on auditory pathways, the purpose of this study was to compare the latency and amplitude of (AEBR) in full-term and premature neonates. Materials and Methods: This cross-sectional study was conducted on 40 full-term and 40 premature neonates (1 -28 days). The obtained amplitude and latency of AEBR were studied. The data were analyzed using SPSS software and t- test . Results: While the mean latency of I, III, V waves and inter-wave latency of I-III, I-V, III-V and also amplitude of V waves showed a significant difference in both groups, the comparison of amplitude of waves I in two groups showed no significant difference. Conclusion: According to the availability of a significant difference between the latency and amplitude of auditory brainstem responses in full-term and premature newborns, and due to the delayed maturation of central auditory nervous system, the use of relative normative data for the study of auditory-evoked potentials in premature neonates are suggested