Functional Analysis of a Proline-Rich Protein, EARLI1, in Conferring Protection Against Low Temperature Stress in Arabidopsis thaliana

Wenxian Tan
Marquette University
Milwaukee, WI
Mentor: Dr. Michael Schläppi

Understanding what effects environmental factors have on crop plants, and how these effects mediate plant development and viability may have serious large-scale socio-economical implications. Among many factors that are taken into account in the determination of suitable crop plants is climate (i.e. temperatures, humidity, seasons). In the United States, frost is one of the main causes of crop damage and can cause serious damage to the size of a harvest as well as having economical ramifications. As some plants do better than others in lower temperatures, understanding how protection is conferred to these plants may allow us to better crop plants by making them more resistant to freezing damage.

EARLI1, a protein with a proline-rich domain, has been shown to be induced under low temperature conditions in Arabidopsis thaliana. Freezing-induced damage is believed to occur primarily at the plasma membrane. We have preliminary data that shows that EARLI1 localizes to the plant cell peripheral regions, suggesting that this protein may function by stabilizing the plasma membrane during low temperature stress. 

As a preliminary test of this hypothesis, EARLI1 expression was manipulated by either up-regulation or down-regulation, and the effects of the manipulations versus the wild type plants were observed. Tests were performed on unacclimated plants and then repeated on plants that had been cold-acclimated for a week at 4°C. Plants of all backgrounds were subjected to electrolyte leakage assays to test if the manipulation of EARLI expression affected the integrity of the plasma membrane when subjected to freezing stress. We also wanted to determine if the up-regulation or down-regulation of EARLI1 affected the viability of plants subjected to freezing. Whole plant survival assays were conducted on all backgrounds and survival was quantified by the number of plants alive a week after treatment. 

Early data shows that while the resistance of unacclimated EARLI down-regulated plants is comparable to wild type plants before acclimation, cold acclimated EARLI1 down-regulated plants are less resistant to freezing stress than wild type plants after cold acclimation. We also have data showing that unacclimated EARLI1 up-regulated plants have a higher resistance to freezing stress than unacclimated wild type plants, while acclimated wild type and EARLI1 up-regulated plants have comparable resistance to freezing stress. These findings support the hypothesis that EARLI1 may play a role in stabilizing the plasma membrane of a cell during low temperature stress. 
 
 
 
 

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