Michael Thomashow

  • Core Faculty, Plant Defense Faculty, Plant models

University Distinguished Prof, MSU Foundation Professor

Dept. of Plant, Soil and Microbial Sciences
Dept. of Microbiology and Molecular Genetics
thomash6@msu.edu

Research: Plant Responses to Abiotic Stress

Abiotic stresses including extremes in temperature and water availability are major factors that determine the natural geographical distribution of plants and limit agricultural production on an annual basis. Our overarching interest is to understand the mechanisms that plants have evolved to tolerate abiotic stresses and use this information to improve the yield of crops used for food and bioenergy.

Much of our work has focused on cold acclimation, the process whereby plants increase in freezing tolerance in response to low non-freezing temperatures. In early work, we described the CBF cold-response pathway, a highly conserved regulatory network that imparts freezing tolerance (Figure 1). The pathway comprises two primary components: the CBF genes, which encode closely related members of the AP2/ERF family of transcriptional activators, and the CBF target genes, known as the CBF regulon. In Arabidopsis, CBF1, CBF2 and CBF3 are induced within 15 min of exposing plants to low temperature, followed at about 2 h by induction of more than 100 CBF regulon genes. Expression of the CBF regulon leads to increased levels of sugars and proteins with cryoprotective properties that contribute to an increase in plant freezing tolerance.

CBF gene pathway
Figure 1: The Arabidopsis CBF Cold-Response Pathway.

 

Our recent studies on the CBF pathway have focused on regulation of the CBF genes by the CAMTA transcription factors (Doherty et al., 2009, Plant Cell; Kim et al., 2013, Plant J), the circadian clock (Dong et al., 2010, PNAS) and photoperiod (Lee & Thomashow, 2012, PNAS). Current efforts are directed at determining whether the CBF pathway contributes to the natural variation in freezing tolerance observed in Arabidopsis ecotypes from Italy and Sweden (Gehan et al., 2015).

We have also initiated a new line of investigation studying photosynthetic acclimation to low temperature (Figure 2). When Arabidopsis and other chilling tolerant plants are exposed to low temperature, the rate of photosynthesis initially drops, but with time, it recovers in a process called photosynthetic acclimation. In addition, the photosynthetic efficiency of leaves developed at low temperature is much greater than those developed at warm temperature. Very little is known about the genetics of this acclimation process. Thus, our goal is to identify genes that have key roles photosynthetic acclimation to low temperature and to determine their mechanisms of action. We are addressing this issue, taking advantage of the novel high-throughput, non-invasive “phenometrics” technologies developed by David Kramer and colleagues, with the support of Michigan State University, establishing the Center for Advanced Algal and Plant Phenotyping (CAAPP) and research funds from DOE-BES and other DOE programs.

Photosynthetic Acclimation to Low Temperature. 
Figure 2:  Photosynthetic Acclimation to Low Temperature. Photosynthetic efficiency (?II) was measured in 5 Arabidopsis accessions grown at 22°C (Day -2) and then transferred to 5°C for the indicated number of days (Day 0 to 35) and then returned to  22°C.  False color images of plants ranging from highest values (red) to lowest values (blue).