School of Biological Sciences

The University of Hong Kong

Professor M. L. Chye
Wilson and Amelia Wong Professor in Plant Biotechnology

MLC

Tel. +852 2299-0319

M.L. Chye, the Wilson and Amelia Wong Professor in Plant Biotechnology at HKU, completed her PhD on a Commonwealth Scholarship at the University of Melbourne and received postdoctoral training in Plant Molecular Biology at the Rockefeller University (New York) and the Institute of Molecular and Cell Biology (Singapore). She joined the University of Hong Kong in 1993 and was promoted to Professor in 2005. Her administrative roles have included being an Associate Dean (April 2010-April 2016) and Dean (May 2016-August 2019) of the Graduate School.

Listed as a top 1% cited scholar at HKU 2013-2020 (http://hub.hku.hk/local/top1pc/top1pc.jsp), her research awards include an Edward Clarence Dyason Universitas 21 Fellowship (2004/05), an Outstanding University Researcher Award (2006/07), a Croucher Senior Research Fellowship (2007/08), and an Eileen Mary Harris Scholarship (2013). She currently serves as an Associate Editor for Planta (Springer) and Plant Molecular Biology (Springer), and was Chair of the 4th Asian Symposium on Plant Lipids (2011) and the 12th International Symposium on Biocatalysis and Agricultural Biotechnology (ISBAB) in 2016. She works with current international research collaborators from Australia, Canada, China, France, and the UK, as well as local collaborators in two AoEs (AoE/M-05/12 and AoE/M-403/16).


Laboratory of Plant Molecular Biology

Research Team

 


Research Interests

The main focus of the Chye Lab is to understand the function and mechanism of action of stress-induced plant proteins, particularly plant acyl-CoA-binding proteins (ACBPs). We intend to use them to generate transformed plants that can better tolerate abiotic and biotic stresses since these stresses account for ~40 % loss in crop productivity. Ultimately, investigations on plant ACBPs, and others, will be applied to agriculture and phytoremediation.

Our projects are supported by the Wilson and Amelia Wong Endowment Fund, Research Grants Council of Hong Kong, NSFC/RGC Joint Research Scheme, “Centre for Organelle Biogenesis and Function” Area of Excellence AoE/M-05/12 (http://www.cuhk.edu.hk/centre/iCell/), “Centre for Genomic Studies on Plant-Environment Interaction for Sustainable Agriculture and Food Security” Area of Excellence AoE/M-403/16” (https://aoegspei.cuhk.edu.hk/aboutus/) and the State Key Laboratory of Agrobiotechnology (CUHK).

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Arabidopsis acyl-CoA-binding proteins (ACBPs) and stress tolerance

We are studying a family of plant ACBPs which bind acyl-CoA esters and transport them within the plant cell. In Arabidopsis and rice, six genes encode four structurally distinct classes of ACBPs (Leung et al., 2004; Xiao and Chye, 2009; 2011b; Meng et al., 2010; 2014). In Arabidopsis the six members are

Arabidopsis ACBP2 is expressed in the guard cells

ACBP2 overexpression in transgenic Arabidopsis enhances drought tolerance

  1. 10-kDa cytosolic ACBP of which homologues have been well-characterized in other eukaryotes (Chen et al., 2008),
  2. membrane-associated ACBPs with ankyrin repeats, ACBP1 and ACBP2 (Chye et al., 1999; Li and Chye, 2003; 2004; Xiao et al., 2008a; Chen et al., 2010; Gao et al., 2009; 2010; Du et al., 2010, 2013a, 2013b),
  3. ACBP3 (Leung et al., 2006; Xiao et al., 2010; Xiao and Chye; 2010, 2011a; Zheng et al., 2012) and
  4. cytosolic kelch-motif containing ACBP4 and ACBP5 (Leung et al., 2004; Li et al., 2008; Xiao et al., 2008b; 2009).

 

In our attempt to understand the function of Arabidopsis ACBPs, we have identified the amino acid residues in the acyl-CoA-binding domain that are important in binding acyl-CoA esters (Chye et al., 2000; Leung et al., 2004; 2006). Some ACBPs can also bind phospholipids (Chen et al., 2008; Du et al., 2010; Chen et al., 2010; Xiao et al., 2010). On lipid analysis, Arabidopsis acbp mutants and transgenic Arabidopsis lines overexpressing ACBPs showed alterations in lipid composition (Xiao et al., 2008b; 2010; Chen et al., 2008; 2010; Du et al., 2010, 2013a, 2013b). ACBPs with ankyrin repeats (Li and Chye, 2004; Gao et al., 2009; 2010; Du et al., 2013b) and kelch motifs (Leung et al., 2004; Li et al., 2008; Xiao et al., 2008b) have been demonstrated to mediate protein-protein interactions.

 

We have observed that certain ACBPs are induced by various forms of abiotic and biotic stresses (Xiao et al., 2008a; Li et al., 2008; Chen et al., 2008; Gao et al., 2009; 2010; Xiao and Chye; 2010, 2011a; Zheng et al., 2012; Du et al., 2013a, 2013b). Subsequently, when these ACBPs were overexpressed in transgenic plants, the resultant lines were conferred stress tolerance. ACBP6-overexpressors were freezing tolerant (Chen et al., 2008; Liao et al., 2014; US Patent No. 8378172) and ACBP2-overexpressors were drought tolerant (Du et al., 2013b; US Patent Application 13,667,569). ACBP1- and ACBP2-overexpressors also displayed tolerance to heavy metal and oxidative stresses (Xiao et al., 2008; Gao et al., 2009; 2010; Du et al., 2014). Interestingly, ACBP1-overexpressors accumulate Pb(II) in shoots making ACBP1 applicable for phytoremediation, a low-cost solar-driven process that removes pollutants from the environment in situ (Xiao et al., 2008a, Xiao and Chye, 2008; US Patent No. 7,880,053).

   Pathogen-inducible ACBP3 is expressed in stem phloem (P) and leaf vasculature of transgenic Arabidopsis

Arrested embryo development in the acbp1acbp2 mutantTransgenic Arabidopsis ACBP6-overexpressors are freezing-tolerant

Stress-inducible HMGS, an enzyme in plant isoprenoid metabolism

Brassica juncea

We are investigating the role of 3-hydroxy-3-methylglutaryl-CoA synthase (HMGS) in plant isoprenoid metabolism. HMGS is an enzyme in the cytosolic mevalonate pathway which produces sterols, sesquiterpenes and polyterpenes. Its expression is stress-inducible and is highest during early development in flower, seed and seedling (Alex et al., 1999). Four isogenes encoding HMGS are differentially expressed in Brassica juncea (Nagegowda et al., 2005).

Using green fluorescent protein fusions, B. juncea HMGS1 (BjHMGS) has been subcellularly localized to the cytosol (Nagegowda et al., 2005). We have biochemically purified and characterized His-tagged recombinant BjHMGS expressed in Escherichia coli, presenting a first detailed characterization of a plant HMGS, and the amino acids involved in catalysis were identified by site-directed mutagenesis (Nagegowda et al., 2004). In collaboration with the Bach Lab and the Noel Lab, the crystal structure of Brassica HMGS covalently bound to specific inhibitor F-244 has been determined, providing a first approach towards the design of more potent cholesterol-lowering drugs and antibiotics that target the mevalonate pathway (Pojer et al., 2006).

When mutant and wild-type BjHMGS were expressed in transgenic Arabidopsis, the genes of the sterol biosynthetic pathway were upregulated resulting in an overaccumulation of phytosterols (stimasterols, campesterol and stigmasterols), and the HMGS-overexpressing lines were better protected against oxidative stress and Botrytis infection (Wang et al., 2012). Furthermore, the overexpression of HMGS variant S359A in a model plant from the family Solanaceae, not only resulted in phytosterol accumulation but showed enhanced plant growth, pod size and seed yield (Liao et al., 2014; US Patent Application 14/260,561). The potential of S359A in boosting seed yield may now be tested in food crops.


HKU Press releases:

HKU plant scientists identify a new strategy to enhance rice grain yield (1/12/19)
https://www.hku.hk/press/press-releases/detail/20327.html

HKU researchers generate tomatoes with enhanced antioxidant properties by genetic engineering (9/11/17)
https://www.hku.hk/press/news_detail_17055.html

Enhancing drought tolerance in plants:
Nikkei Asia Review (13/1/16) http://asia.nikkei.com/Tech-Science/Science/Hong-Kong-scientists-engineer-plants-for-a-warmer-planet

HKU scientists discover a drought tolerance gene that may help plants survive global warming (22/11/15):
http://www.hku.hk/press/press-releases/detail/13590.html

HKU identifies a new strategy to protect flowers from freezing stress (9/6/14):
http://www.hku.hk/press/press-releases/detail/11311.html


Representative Publications

 

Last modified: 27/12/2018


Please send suggestions and comments to mlchye@hku.hk.