Departments of Plant Biology and Horticulture, MSU
How do plants respond to environmental stresses?
Environmental abiotic stresses, such as cold, drought, and high salinity, can greatly affect plant growth and development. Plant scientists have faced increasingly challenging climate changes to maintain and increase the food production in the world. Due to their sessile nature, plants have to develop special systems to respond and adapt to stresses and ultimately acquire stress tolerance for survival. Thus, understanding mechanisms for stress adaptation and tolerance is one of the most important and challenging goals in plant sciences and holds the key for future plant breeding. One of our main ongoing research projects is to identify plant “enhancers” that regulate expression of genes activated by abiotic stresses. Enhancers are cis-regulatory DNA elements that control the expression of genes during specific developmental stages or under various biotic and abiotic stresses. Enhancers can be identified based on their unique molecular signatures associated with open chromatin (2015, Plant Cell 27: 2415-2426). Identification and characterization of stress-responsive enhancers will be essential for us to understand plant stress biology, such enhancers will also become a key resource to improve the tissue specificity and transcription levels of transgenes for crop improvement.
A cold-inducible enhancer in Arabidopsis thaliana. The two transgenic plants carry the same T-DNA insertion composed of an enhancer fused to the GUS reporter gene. Left: GUS assay of a two-week-old seedling grown under room temperature. Right: GUS assay of a seedling placed under 4o C for 24 hours prior to GUS staining. Note: GUS signals were mainly observed in roots and main veins before cold treatment. GUS signals can be observed in the entire seedling after cold stress.
Plant centromeres: a model for plant epigenetic research
An “epigenetic phenomenon” typically refers to a trait or a phenotypic change that is not caused by DNA sequence change, but by “epigenetic changes”, including DNA methylation, histone modifications and dynamics of non-coding RNAs. Epigenetic changes have been found to be widely associated with plant growth, development, and survival from biotic and abiotic stresses. Centromeres provide a unique model system for epigenetic research. The centromere is specified by the presence of a special histone H3 variant, CenH3. Interestingly, the establishment and maintenance of centromeres is not defined by the underlying DNA sequences, but rather are determined by poorly understood epigenetic mechanisms. Centromeres in most plants contain highly repetitive DNA sequences that evolve more rapidly than the rest of the genome (2012, Plant Cell 24: 3559-3574). Most interestingly, a centromere can be inactivated by losing its CenH3 (2010, Chromosoma 119: 553-563), activated in a non-centromeric region by gaining CenH3, or expand its size in a different genetic background (2014, Genome Res. 24: 107-116). We are interested in the epigenetic changes that may play a role in centromere function and evolution.
Centromere inactivation. The arrows indicate the same wheat dicentric chromosome. The chromosome on the right contains a big (arrow) and a small (arrowhead) centromere. However, the small centromere on the left chromosome was inactivated by the loss of CenH3 (red signals). It is unknown what causes the loss of CenH3 and subsequent centromere inactivation. However, inactivation is always associated with the smaller of the two centromeres.