Discipline: Ecology Environmental and Earth Sciences
Subcategory: Plant Research
Mayla Ayers - Harris-Stowe State University
Co-Author(s): He Huang, Donald Danforth Plant Science Center, St. Louis, MO
Global warming hinders agricultural development by increasing temperature stress on plants. With temperatures steadily increasing, plant growth is altered. In order to overcome this challenge, we aim to design strategies to genetically modify plants to improve their performance in response to elevated temperatures. Light and temperature are perceived by a key protein called phytochrome B (phyB) that serves as the major red-light photoreceptor and temperature sensor that directly converts environmental signals to regulate growth. Active phyB negatively regulates the activity of a transcription factor PHYTOCHROME INTERACTING FACTOR 4 (PIF4), which promotes growth under low light and high temperature conditions. Recently, the Nusinow lab has identified a novel phyB regulator named PCH1 (PHOTOPERIODIC CONTROL OF HYPOCOTYL1). PCH1 is a newly identified gene that controls light sensing by increasing red-light signaling through phyB. To test if PCH1 plays a critical role in regulating thermoresponsive plant growth, we determined if altering PCH1 levels broadly affected plant growth under elevated temperature conditions. Preliminary data suggests that pch1 increased plant growth in the long day condition (light : dark = 16 hours : 8 hours) with higher temperatures (28°C), while PCH1ox3 decreased plant growth. We also sought to determine the genetic relationship between PCH1 and PIF4. Since PIF4 is a downstream target of phyB, we expect that if PCH1 only functions through a linear pathway, the double mutant (pif4-pch1) would resemble the single pif4 mutant. If not, then the double mutant would resemble that of the pch1 mutant. We compared five-day-old wildtype, pch1 (loss of function mutant), PCH1ox3 (overexpression of PCH1 protein), PCH1pro::PCH1 (PCH1 complementation line), pif4 (loss of function mutant), and pch1-pif4 (loss of function double mutant). After stratification in the dark at 4˚C for 48 hours, seeds were then put into a growth chamber in a short day (light vs. dark = 8:16) condition or an LL (light vs. dark = 24:0) condition with the temperature set as either 22°C or 28°C to eliminate the effects of the photoperiod. As expected, the pif4 mutant was shorter in both temperatures in the LL condition as well, resembling wildtype. However, the pch1 mutant has a longer hypocotyl than wildtype in 28°C but not in 22°C in the short day condition. Unexpectedly, the double mutant pch1-pif4 is significantly longer than wildtype and the other mutants in both temperatures under the constant light condition. We can suggest that PCH1 has a likely independent role on the phyB-pathway because PIF4 is not epistatic to PCH1 in this condition. LL condition causes the plant to already reach the strongest suppression of hypocotyl therefore the effect of PCH1ox3 can be masked by the LL condition. We would like to further test any unknown independent components to the system in which the hypocotyl growth still persists without PIF4.
Funder Acknowledgement(s): National Science Foundation; Research Experiences for Undergraduates
Faculty Advisor: Dr. Dmitri Nusinow, firstname.lastname@example.org
Role: I organized and sterilized the Arabidopsis thaliana seeds in a bleach and detergent solution to pipette them onto the MS + 1% sucrose agar plates for stratification. I transferred twenty Arabidopsis seedlings of genetic varieties to non-grid plates using tweezers. On this plate, I cut the cotyledon from the hypocotyl using precision scissors. The separated cotyledon pairs were then placed onto non-grid agar plates, flattened for imaging and then uploaded onto imaging software ImageJ to calculate the area in square mm. I also collected measurements of the hypocotyl through this software.