Maria Hrmova

Professor Maria Hrmova

Professor

School of Agriculture, Food and Wine

Faculty of Sciences


Professional interests – my expertise is in the multidisciplinary field of structural biochemistry and biophysics.

Research in my group resulted in publishing over 140 peer-reviewed articles and patents on mechanisms explaining plant abiotic stress tolerance and enzyme catalysis. Our papers have appeared in the top-tier journals Nature Communications, Science, American Chemical Society, Biotechnology Advances, Plant Cell and Current Opinion in Plant Biology. Our papers received ~5,500 citations and 18 papers were featured on front covers.

My group investigates molecular mechanisms that underpin the function of plant proteins in three major areas:

(i) PLANT TRANSPORT PROTEINS UNDERLYING ELEMENTAL SOIL TOXICITY TOLERANCE

My laboratory is focused on the structural and functional properties of plant borate and HKT (High-affinity Potassium Transporter) Na+/K+ transporters, and on orthodox and multifunctional aquaporins. By combining in silico and in vitro methods, we discovered that borate transporters mediate Na+-dependent anion transport and exhibit channel-like characteristics. This work was published in Plant Cell, one of the highest-ranking journals in the plant science field.

With HKT transporters, we designed a model for Na+-exclusion in rice and explained that variations in salt tolerance can be explained by transcription, alternative splicing and a protein structure. We also clarified a long-standing question, how the structural variations in wheat HKT proteins underpin differences in Na+ transport capacity; this work was highlighted on the front cover of Cellular and Molecular Life Sciences.

(ii) TRANSCRIPTION FACTORS INVOLVED IN THE REGULATION OF PLANT RESPONSES TO DROUGHT

We perform extensive 3D molecular modelling studies of transcription factors in complex with DNA cis-elements, such as bZIP, HDZip, DREB, ERF, NFY-YB, CBF and MYB, and validate these DNA-binding properties in vitro. We engineered wheat transcription factor variants and in the breakthrough science, using genetically engineered plants, we showed that these modifications changed DNA recognition and plant responses to drought and frost. Our work has been featured on the front covers of Plant Biotechnology Journal, Plant Molecular Biology and Journal of Experimental Botany.

(iii) CATALYTIC MECHANISMS OF ENZYMES INVOLVED IN PLANT DEVELOPMENT

We focus on exohydrolytic enzymes to define their catalytic mechanisms at the atomic levels. We solved the crystal structure of a plant exohydrolase with a non-covalently trapped glucose product, but the glucose displacement mechanism, and how it is linked to the catalytic cycle remained unanswered. Using high-resolution X-ray crystallography, enzyme kinetics, mass spectrometry, NMR spectroscopy and multi-scale 3D molecular modelling, we revealed the new catalytic mechanism that we coined "substrate-product assisted processive catalysis”. Here, upon productive substrate binding near the active site, entrapped glucose modifies its binding patterns and evokes the formation of a temporary lateral cavity, which serves as a conduit for glucose departure to allow for the next catalytic cycle. This path enables efficient catalysis via multiple hydrolytic events without the enzyme losing contact with oligo- or polysaccharides. This discovery has significance in biotechnology to engineer enzymes that could be used efficiently outside of biological systems. This work was published in Nature Communications.

Using a combination of biology, biochemistry, biophysics, bioinformatics and computational chemistry techniques, including  multi-scale molecular modelling of nanoscale reactant movements in a plant exohydrolytic enzyme, we have discovered a remarkable phenomenon during initial and final catalytic events near the surface of this enzyme. The enzyme formed a transient cavity, which allowed the trapped glucose product to escape to allow for the next round of catalysis. This path enables "substrate-product assisted processive catalysis" through multiple hydrolytic events without the enzyme losing contact with oligo- or polymeric substrates. We anticipate that such enzyme plasticity could be prevalent among exo-hydrolases.

Our discovery the substrate-product assisted processive catalysis has significance in for the multibillion dollar biomedical, pharmaceutical, chemical and biotechnology industries to engineer enzymes that could be used efficiently outside of biological systems.

This work was published in Nature Communications.

Streltsov VA, Luang S, Peisley A, Varghese JN, Ketudat Cairns JR, Fort S, Hijnen M, Tvaroška I, Ardá A, Jiménez-Barbero J, Alfonso-Prieto M, Rovira C, Mendoza F, Tiessler-Sala L, Sánchez-Aparicio S-E, Rodríguez-Guerra J, Lluch JM, Maréchal J-D, Masgrau L, Hrmova M* (2019) Discovery of processive catalysis by an exo-hydrolase with a pocket-shaped active site. Nature Communications 10, 1-17; DOI: https: //doi.org/10.1038/s41467-019-09691-z. *Corresponding author.

Press Release to this article can be seen here .

A movie describing the newly discovered catalytic mechanism can be seen here :

Movie description:

Molecular animation of the sequence of events involving the glucose product entrapment, incoming substrate binding and glucose displacement in a plant exo-hydrolase HvExoI, and how this sequence of events underlies substrate-product assisted processive catalysis. The movie shows the entrapped glucose molecule in the -1 subsite of the active site, through twelve residues located on seven loops. After the incoming β-D-glucopyranosyl-(1,3)-D-glucose substrate binds in the +1 and putative +2 subsites, the glucose product adjusts its binding patterns and traverses from the -1 subsite through rotations of Arg158 and Asp285 sidechains and associated backbone atoms, into the autonomous and transient lateral cavity, from where it advances through the aperture into the bulk solvent. The video was prepared in Chimera (Pettersen, E. F. et al. J. Comput. Chem. 25, 1605-1612; 2004), using the HD Movie Maker tool.

Research in my laboratory has been funded by grants from the Australian Research Council, by the Grains Research & Development Corporation, the South Australian Government, the Waite Research Institute of the University of Adelaide, DuPont Pioneer and by the Australian Synchrotron Research Program. The latter is supported by the Commonwealth of Australia under the Major National Research Facilities Program.

I have successfully completed supervisions of 25 doctoral (PhD), masters (MSc) and honours (BSc) candidatures by research. My students have received a variety of awards: Best Presentation in Plant Science and runner up for the Max Tate Award (in-house Annual Postgraduate Symposium), People’s Choice (3-minute PhD thesis competition), Travelling Scholarship to Cambridge University (Barr Smith Foundation), the KP Barley Prize for PhD thesis excellence (Faculty of Sciences), and CJ Everald and GRDC top-up scholarships.

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  • Past Higher Degree by Research Supervision (University of Adelaide)

    Date Role Research Topic Program Degree Type Student Load Student Name
    2012 - 2016 Co-Supervisor Characterization of Wheat Cuticle and Wheat Cuticle-Related Transcription Factor Genes in Relation to Drought Doctor of Philosophy Doctorate Full Time Miss Huihui Bi
    2011 - 2015 Principal Supervisor Structural and functional properties of a borate efflux transporter from barley Doctor of Philosophy Doctorate Full Time Dr Yagnesh Nagarajan
    2008 - 2017 Co-Supervisor The Evolutionary History and Dynamics of the Cellulose Synthase Superfamily Doctor of Philosophy Doctorate Full Time Dr Julian Schwerdt
    2004 - 2008 Co-Supervisor Characterisation of PpMDHARs and PpENA1 From the Moss, Physcomitrella patens Doctor of Philosophy Doctorate Full Time Mr Damian Drew
    1997 - 2002 Co-Supervisor Biochemistry and Molecular Biology of Arabinoxylan Metabolism in Barley Doctor of Philosophy Doctorate Full Time Mr Robert Lee
  • Position: Professor
  • Phone: 83137160
  • Email: maria.hrmova@adelaide.edu.au
  • Fax: 8313 7102
  • Campus: Waite
  • Building: Plant Genomics Centre, floor 2
  • Room: 2 36
  • Org Unit: Australian Centre for Plant Functional Genomics (ACPFG)

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