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A new species of reddish-orange pigment-producing microalga was isolated from a shallow pond in tropical Taiwan. Morphological and molecular evidence including meridional ribs on the cell wall, pigment production, and 18S rDNA sequence analysis suggest that this microalga is a species in the genus Coelastrella. Salt stress accelerated biosynthesis of the reddish-orange pigments, and large quantity of oil accumulated as the cells stressed under nutrient deficiency. This microalga could sustain 45 ¢XC for more than 8 hours indicated by the stability of its chlorophylls, which is a necessary trait for large scale outdoor cultivation using photobioreactors in tropical areas. The reddish-orange pigments could be separated into many fractions by HPLC, and signals from carotenoids were detected in a few fractions using NMR, suggesting these pigments may function as antioxidants among other roles.

The ArsA homologue ARR4 in Saccharomyces cerevisiae, encoded by YDL100C. Homologues of the E. coli ArsA are found in S. cerevisiae about 29 % from Genetic Computer Group (GCG). The ARR4 gene product contains an ATP binding site that is similar to protein ArsA from E. coli Disruption of ARR4 in yeast is not lethal but the disrupted strain was unable to grow at 40¢J, suggesting that the possible cause of cell death in KO strain at 40¢J was investigated. The accumulation of trehalose and the in vivo molecular oxidation level are higher in KO strain than that in WT strain under heat stress condition. These suggest that the increased reactive oxygen species (ROS) but not the amount of thermoprotectant trehalose is most likely to be the reason for cell death in KO strain. In this report ROS scavenger system show that the activities of ROS scavenger system are lower in KO compared to that in WT strain at 30¢J or 40¢J. This suggests that ARR4 is involved in the heat stress ¡Boxidative stress and osmatic stress triggers activation of the STRE ( stress tolerance response element) regulon. Further studies involvement ARR4 of CTT1, SOD1, and TSL1 gene of STRE-drive gene by RT-PCR. Here the report that the KO strain exhibits a thermosensitivity phenotype in comparison to wild-type strain, indicating that ARR4 may act as a component of a stress tolerance network.

Exercise in hot environments decreases the temperature gradient for heat loss to the external environment increasing internal heat storage. Work completed decreases and exertional heat illness risk increases. Heat acclimation (HA) programmes which last between 7 -10 d improve heat tolerance by reducing rectal temperature (Tre) during exercise. Thermotolerance is also improved. These adaptations enable work to be maintained for longer periods of time. Exertional heat illness risk is also decreased. However, HA is not logistically feasible during rapid redeployment of military, athletic, occupational and emergency worker populations to hot environments. Therefore, developing an acute preconditioning trial to enhance heat tolerance and thermotolerance could be advantageous. This thesis first determined the effect of treadmill gradient (flat or downhill running) and environmental conditions (temperate~ 20oe, 50 % relative humidity (RH) or hot conditions; 30°C, 50 % RH) on heat shock protein 72 mRNA (Hsp72 mRNA), heat shock protein 90 alpha mRNA (Hsp90a mRNA), glucose regulated protein 78 mRNA, glucose regulate protein 94 mRNA, exercising Tre and HR, Study 2 investigated whether an acute trial combining downhill running and hot environmental conditions (Hot downhill) elevated basal HSP72 concentrations, attenuated exercising Tre• HR, vastus lateralis (VL) and leukocyte Hsp72 mRNA and Hsp90a mRNA responses during an identical trial 7 d later. Downhill running and hot environmental conditions increased leukocyte Hsp72 mRNA, leukocyte Hsp90a mRNA, exercising Trc and DOMS further than flat running and temperate environmental conditions. Increased Hsp72 mRNA and Hsp90a mRNA were mainly exercising Tre and metabolic strain dependent. Exercising Tn; (at 30 min) and DOMS were reduced during or following the second hot downhill trial. Attenuated Hsp72 mRNA and Hsp90a mRNA responses within the VL and leukocytes also occurred. Basal VL HSP72 increased after the second hot downhill trial In conclusion, an acute hot downhill trial decreases exercising Tn: and DOMS during an identical trial 7 d later but basal HSP72 concentrations are not affected. Leukocyte Hsp72 mRNA and Hsp90a mRNA are valid surrogates of the VL response.

Coral reefs are in global decline due to ocean warming and ocean acidification. While these stressors are commonly studied in climate change predictions, salinity, although being an important environmental factor, is not well understood. The response of the coral holobiont (the association of the coral host, its algal endosymbiont and a suit of other microbes) to changes in salinity and the contribution of each holobiont compartment underlying the necessary osmoadaptation remain especially elusive. Interestingly, we find some of the most thermotolerant corals in some of the most saline seas, e.g. the Red Sea and the Persian Arabian Gulf. This observation sparked the hypothesis of a link between osmoadaptation and coral thermotolerance. Here, we set out to elucidate the putative effects of high salinity on conveying thermotolerance and thereby a possible link to bleaching in the context of the coral holobiont. For this, we conducted a series of heat stress experiments at different salinities in the coral model Aiptasia and subsequently validated our findings in corals from the central Red Sea. We confirm a role of osmoadaptation in increased thermotolerance and reduced bleaching in Aiptasia and Red Sea corals. This salinity-conveyed thermotolerance was characterized by a reduction in algal endosymbiont loss, photosystem damage and leakage of damaging reactive oxygen species (ROS) in high salinity. Further analysis of the osmoadaptation response using targeted GC-MS uncovered high levels of the sugar floridoside at high salinity only in holobionts that show the salinity-conveyed thermotolerance. The increase of floridoside, an osmolyte capable of scavenging ROS, and the concurrent reduction of ROS argues for a mechanistic link of increased thermotolerance and reduced bleaching in high salinities. In addition, the restructuring of the microbiome at high salinity that aligned with the difference in thermotolerance in Aiptasia may be indicative of a microbial contribution towards a more beneficial holobiont composition. Hence, emphasizing the potential cumulative contribution of each holobiont compartment during stress-resilience, as well as highlighting the overall role of osmoadaptation in the thermotolerance of corals.

Temperature is a major abiotic stress limiting plant growth. Thermotolerance evaluation during germination and early growth may help identify adaptable genotypes of new crops. Two studies were conducted to evaluate temperature effects on 12 Brassica carinata genotypes during germination and early growth. During germination, genotype AX17004 was both the most cold- and heat-tolerant. During early-season growth (35 d after seeding), there were temperature and genotype effects on shoot, root, and physiological components. Cumulative low- and high-temperature response indices, and cumulative root and shoot response indices were related, indicating the importance of these traits. Genotype AX17006 was identified as heat tolerant, and AX17009 as cold tolerant during early-season growth. When genotypes were grouped according to breed types, hybrids generally had better responses than the inbred lines, and double haploids and the check responses were intermediate. These studies provided rapid results that will reduce the number of genotypes assessed in field studies.

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Gametophytic selection was examined as a breeding tool in developing Phalaenopsis hybrids that are more cool or warm temperature tolerant. Two hybrid Phalaenopsis, P. (Taisoco Windian à Sogo Sogo Yukidian) by P. hybrid unknown, were reciprocally cross-pollinated and exposed to 14°C/9°C for 7 days as a cold pollination treatment. Plants were pollinated again and exposed to 30°C/25°C for 3 days for the warm pollination treatment. Each cultivar was placed in either of two growth chambers during the pollination treatments and exposed to the selected temperatures, an 11-h photoperiod with an irradiance of 180 Mmol·m-2·s-1 and a relative humidity of 70%. The plants were returned to the greenhouse after pollination and the green capsules were collected after 150 days. Seeds obtained from these treatments were surface-sterilized and equal volumes were placed on Phytamax® medium. Evaluation of protocorm development was done after 73 days on a thermogradient table ranging from 10 to 30ºC. For the first family for which reciprocal crosses were available, the number of protocorms per plate ranged from 0 in the coldest treatments to 290 at 28°C. For cold pollinated seeds, protocorm development was optimum at 22 and 28°C (means of 290 and 250 protocorms per plate, respectively) whereas the greatest protocorm development for warm pollinated seeds occurred at 20°C (103 protocorms per plate). Of the 1471 total protocorms obtained 1095 were from cold pollinations, whereas 376 were from the warm pollinations. Protocorms were evaluated for leaf and root formation 125 days after initial plating. Transfer to warm or cold incubators occurred as protocorms developed leaves and roots. Seedlings were finally transferred to dried sphagnum and placed in growth chambers set to original pollination temperatures. One year after initial plating seedlings were evaluated on the following criteria: wet weight, number of leaves, leaf area, number of roots, and root length. The pollination treatment significantly affected the number of roots per seedling whereas germination temperature during germination significantly affected the weight (g). Weight of the seedlings, number of roots and the average root length were significantly affected by the interaction between pollination treatment and germination temperature. The weight, number of leaves, and average root length were significantly affected by the interaction between pollination treatment and incubator/growth chamber. These differences indicated that seedlings derived from warm pollination were more vigorous under warm growing conditions and those derived from cold pollination were more vigorous under cold growing conditions. The significance of the interaction between pollination treatment and incubator/growth chamber indicates that gametophytic selection for thermotolerance in Phalaenopsis can be successfully used as a plant breeding tool. Additional replication is required to confirm the greater germinability of seed derived from pollination occurring over a greater range of temperatures. / Master of Science

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Environmental variation is ubiquitous in natural systems. The genetic and physiological mechanisms governing population-level responses to this variation will impact the process of speciation and the capacity for populations to persist in a changing climate. Until recently, population-level responses to environmental selection remained largely unexplored in marine systems due to the historical assumption that the inherently dispersive nature of most marine taxa would preclude their ability to specialize to local environments. This dissertation represents the first investigation of population-level responses to environmental variation in a Caribbean reef-building coral. This research integrates ecological, physiological, genetic and genomic methods to (1) determine patterns of local adaptation in the Florida Keys, (2) identify stressors driving adaptive responses, (3) distinguish the physiological and genetic mechanisms underlying coral adaptation and (4) assess the potential for future adaptation in the common reef-building coral Porites astreoides. Results demonstrate that corals adapt and/or acclimatize to their local habitat and that this specialization incurs fitness costs. Temperature differences between reefs likely play a selective role in differentiating inshore and offshore coral populations. Genetic and gene expression differences indicate that coral hosts play a substantial role in driving these population-level differences. Inshore corals exhibit greater gene expression plasticity, which may be involved in stabilizing physiological responses to temperature fluctuations experienced at inshore reefs. In addition, naïve juvenile coral recruits from inshore reefs exhibit a growth rate advantage over offshore recruits under elevated temperature treatment, suggesting that thermotolerance differences observed in adult populations could continue to evolve in response to climate change. Taken together these results provide novel insight into the drivers of reef decline in the Florida Keys and the role of the host in coral adaptation capacity. / text