AbstractsBiology & Animal Science

Most studies of plant responses to heat stress examine basal thermotolerance and short-term acquired thermotolerance to high heat. In nature plants experience moderately high temperatures (30????C-38????C) for long periods of time. The goal of this study is to find the effects of long term moderately high temperature heat stress on the two native California species, Boechera arcuata and Boechera depauperata, and compare it to a model organism Arabidopsis thaliana. We measure chlorophyll fluorescents (CF), cell death, and transcriptional fold change for APX2, HSFA2, HSP101, and HSP18.1 to heat stress at 35????C and 38????C. We asked the following three questions: How is the efficiency of Photosystem II (PSII) affected by moderately high temperature heat stress in A. thaliana, Boechera arcuata, and Boechera depauperata? Is cell death under heat stress different between A. thaliana and the two Boechera species? Is gene expression under heat stress different between A. thaliana and the two Boechera species? B. depauperata is the most thermotolerant of the three species; at both heat stress temperatures, PSII does not lose conformation and continues to absorb light and fixate carbon. Ion leakage is minimized and there is very little cell death. Upregulation of APX2, HSFA2, and HSP18.1 only occur after 72 hours of continuous heat stress at 38????C in B. depauperata. HSP101 is upregulated at 1 hour at 35????C, but decays after that, and at 72 hours at 38????C. A. thaliana can withstand 35????C heat stress, but 38????C results in PSII efficiency loss, and cell death. Transcription of APX2, HSFA2, HSP101, and HSP18.1 is upregulated substantially more than the other two species at both heat stress temperatures. B. arcuata is the least thermotolerant of the three species studied. Both 35????C and 38????C have an effect on PSII efficiency and cell death, but 38????C has a larger affect. Transcription of APX2, HSFA2, and HSP101 are upregulated early at 1 hour, but decay and back to the same levels as the control by hour 12. HSP18.1 is not upregulated at 35????C and upregulated at 38????C after 48 hours of continuous stress. All three species handle moderately high temperature heat stress differently. B. depauperata is the most thermotolerant, A. thaliana is the second most thermotolerant, and B. arcuata is the least thermotolerant. These findings can help us better understand and predict the effects of global rise in temperatures on plant species and it can lead to designing better crops to withstand abiotic stress.