Herbert Newby McCoy Award Current Recipient
Jian Kang Zhu – 2016 Herbert Newby McCoy Award
Jian Kang Zhu is a Distinguished Professor of Plant Biology, Departments of Horticulture and Landscape Architecture and Biochemistry at Purdue University, and Director of the Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences. He earned his bachelor's degree in soils and agricultural chemistry from Beijing Agricultural University; his master's degree in botany from the University of California, Riverside, and his doctorate in plant physiology from Purdue. Previously he was at the University of California, Riverside, where he was the Jane Johnson Chair Professor in the Department of Botany and Plant Sciences. Prior to UC Riverside, he spent eight years as a faculty member at the University of Arizona, Tucson. His research has sought to elucidate the signaling pathways in plants that govern their responses to environmental stresses such as drought, soil salinity and freezing temperatures. He is also interested in epigenetics, particularly how the DNA methylation mark is deposited and removed.
Title of Lecture
Decoding the epigenetic language of life
Epigenetics refers to the study of heritable information that is not contained in DNA sequence. An important epigenetic mark conserved in mammals and plants is DNA methylation, a chemical modification of DNA that controls gene function. Proper DNA methylation patterns are critical for development, diseases and stress responses in humans as well as in plants. Plants are excellent biological systems to study how DNA methylation patterns are generated. DNA methyltransferase enzymes that deposit the DNA methylation mark are guided to specific DNA sequences, and DNA demethylase enzymes that remove the DNA methylation mark are also guided to distinctive sequences to erase unwanted DNA methylation. I will describe work in my lab that has shed light on how DNA methyltransferases and demethylases are guided to specific sequences, and how the antagonistic actions of the enzymes are coordinated to generate proper DNA methylation patterns. I will also describe some of our recent work on how DNA methylation influences transgenerational inheritance.
- Elucidated the biochemical pathway for the erasure of DNA methylation marks
- Discovered a protein complex that targets DNA demethylases to specific genomic regions
- Proposed the concept of a methylstat that senses and regulates genomic DNA methylation levels
- Demonstrated a role for the RNA-directed DNA methylation pathway in gene allele interactions in hybrid plants
- Identified small chemical molecules with very potent activities in protecting plants from drought stress
Detailed description of research
DNA methylation is a conserved epigenetic mark important for organismal development, diseases and stress responses in plants and mammals. In 2002, Jian-Kang Zhu’s group discovered the first DNA demethylase enzyme, ROS1. This is the long sought after enzyme that functions to erase unwanted DNA methylation marks and prevent DNA methylation-mediated gene silencing. In the last several years, his lab has identified most of the enzymes that function downstream of ROS1 in the base excision repair pathway of active DNA demethylation, including the 3’ DNA phosphatase ZDP, AP endonuclease APE1L and DNA ligase 1. His group designed an innovative genetic screen that resulted in the discovery of an anti-silencing protein complex composed of several regulators of ROS1 function. These regulators include the novel histone acetyltransferase IDM1, alpha-crystallin domain proteins IDM2 and IDM3, the methyl-DNA binding protein MBD7, and two transposon-derived proteins, HDP1 and HDP2. This complex recognizes highly methylated genomic regions and creates histone acetylation marks that allow ROS1 to be recruited to demethylate the genomic DNA. The discovery of this protein complex that regulates demethylase function contributes significantly to our understanding of the targeting of DNA demethylase for precise control of DNA methylation reprogramming during development, stress responses and diseases. Recently, his group elucidated the mechanism of coordination between DNA methylation and demethylation activities, and proposed the concept of a methylstat that senses the DNA methylation and demethylation activities and regulates genomic DNA methylation levels by fine-tuning demethylase gene expression. They found that DNA methylation greatly influences the interaction between some gene alleles in hybrids. In addition, they found a new chemical inhibitor of epigenetic silencing, and identified several new players in the RNA-directed DNA methylation pathway.
In abiotic stress research, his group continues to focus on the signal transduction pathway for abscisic acid (ABA), the most important plant hormone for resistance to drought and other abiotic stresses. His lab contributed to the discovery of ABA receptors and to the elucidation of the structure of the receptor complex, and for the first time achieved the in vitro reconstitution of the core ABA signaling pathway in a test tube. Since joining Purdue, his lab has discovered a unique pathway that plants use to control lateral root growth under stress conditions. They found that one of the ABA receptors, PYL8, interacts directly with a Myb transcription factor in the nucleus and enhances its transcriptional activity to promote lateral root growth, rather than interacting with protein phosphatases in the known core ABA signaling pathway. In collaboration with Prof. Andy Tao’s lab, his group identified several dozens of new proteins that are phosphorylated by ABA-activated SnRK2 protein kinases. These phosphoproteins are important effectors of ABA action in plant cells. Therefore, their identification provided significant new insights into the cellular action of ABA. Recently, his group found that the second messenger nitric oxide (NO) that is induced by ABA, causes S-nitrosylation and inhibition of the SnRK2 kinases. The study revealed how NO functions to desensitize ABA signaling in plants. In addition, his group discovered ABA-mimicking small chemicals that can be applied to plants to activate the ABA pathway to close stomata to reduce transpirational water loss and to induce the expression of drought responsive genes, leading to drought resistance. These chemicals are easy to synthesize, non-toxic, much less expansive and more stable than ABA, and thus have enormous potential for applications in agriculture, turfgrass and horticultural industries to protect plants from drought stress and benefit the environment by reducing the consumption of precious freshwater resources.