Current position
Fellow (ANU)
Directeur de Recherche (INRA, Paris)
Research
My general interest lies in the interplay between genetic and environmental determinants of plant development and morphogenesis. We are studying how plants coordinate cellular proliferation and differentiation within and between organs and generate given patterns and shapes. We are investigating the regulatory networks involved in determining the plasticity of this coordination under abiotic stress and its functional significance.
Our research combines molecular biology and genetics, developmental biology and biophysical approaches, and makes use of both directed genetic manipulation and natural genetic diversity, using Arabidopsis and cereals as main model systems.
Coordination of cellular growth and proliferation, emergence of patterns and plant morphogenesis.
- The function of the Translationally Tumor Controlled Protein (TCTP) in the TOR pathway and plant growth and adaptation. TOR (target of rampamycin) Sr/Thr kinase is a central controller of cellular growth and proliferation in response to external and internal stimuli. In studies of non plant eukaryotes such as yeast, drosophila or mammals, TCTP has been identified as an upstream regulator of TOR. We recently uncovered a role of the Arabidopsis TCTP in leaf growth, root and root hair development and pollen tube growth, consistent with a similar function as in other eukaryotes, as a regulator of TOR activity. We are investigating the molecular and cellular function of plant TCTP and the role TCTP plays in interconnecting growth and the responses to environmental and internal cues.
- The role of ERECTA in leaf organogenesis and functional properties. We discovered that the Leucine-Rich-Repeat Receptor-Like Kinase ERECTA is a central controller of leaf transpiration efficiency, largely through its effects on epidermal development and stomatal density, and also on mesophyll development. We are investigating the molecular and cellular bases of these effects, their regulation and adaptive significance.
- The role of phospholipids and lipid signalling in root development and function. We are interested in phospholipid synthesis and turnover, more specifically PC, the major phospholipid in plants non-plastid cellular membranes, as in most eukaryotes. Besides being a major membrane phospholipid, phosphatidylcholine can be hydrolysed into choline and phosphatidic acid. Phosphatidic acid is widely recognized as a second messenger in stress signalling and choline can be oxidized within the chloroplast to yield the putative osmoprotectant glycine betaine. In plants the triple methylation of phosphoethanolamine to phosphocholine catalysed by phosphoethanolamine N-methyltransferase (PEAMT) is considered a rate limiting step in the de novo synthesis of phosphatidylcholine. Our focus is on this pathway and its role in root development and function.
Developmental controls of the coordination between CO2 fixation and water loss in leaves- Manipulating leaf transpiration efficiency
We are using molecular approaches and natural genetic diversity studies in Arabidopsis to search for genes controlling water use efficiency ie how efficient leaves are in trading water for carbon. We are specifically interested in the networks controlling the coordination of leaf epidermis and mesophyll development/anatomy and in their modulation by environmental cues, especially drought induced root signals and variations in atmospheric CO2.
In this context, we are investigating the role of ERECTA genes in leaf diffusive properties and water use and examining their potential to manipulate transpiration efficiency in crop species.
We are also characterising novel “hot” transpiration efficiency mutants identified through thermal imaging of leaves and measurements of carbon isotope discrimination.
The sensing and signalling of mechanical stress by roots- Genetic regulation of root:shoot communication and function under drought
Roots have evolved sensitive mechanisms for sensing variations in their environment and effective local and long-distance signalling mechanisms. We study the sensing and signalling of root mechanical stress, a condition inevitably associated with soil drought. We examine the developmental and functional responses it triggers in roots and leaves. We have identified a range of mechano-sensitive genes that fall in a range of functional groups including hormonal signalling, meristem function, root development, carbon metabolism and wall synthesis. We are currently characterising some of those genes through the study of a range of mutants and genetic material we have generated in both Arabidopsis and cereals (wheat and or rice).
Selected Publications
Jost R, Berkowitz O, Shaw JE, Masle J. 2009. Biochemical characterisation of two wheat phosphoethanolamine N-methyltransferase isoforms with different sensitivities to inhibition by phosphatidic acid. Journal of Biological Chemistry, First Published online doi:10.1074/jbc.M109.022657.
Berkowitz O, Jost R, Pollman S and Masle J. 2008. Characterisation of TCTP, the translationally controlled Tumor Protein, from Arabidopsis thaliana. Plant Cell, 20:3430-3447.
Hoque MS, Masle J, Udvardi MK, Ryan PR, Upadhyaya NM. 2006. Over-expression of the rice OsAMT1-1 gene increases ammonium uptake and content, but impairs growth and development of plants under high ammonium nutrition. Functional Plant Biology, 33:153-163.
Masle J, Gilmore
SR, Farquhar GD. 2005 The ERECTA gene
regulates plant transpiration efficiency in Arabidopsis.
Nature, 436, 866-870
Buer CS, Wasteneys GO, Masle J. 2003. Ethylene
modulates root wave responses in Arabidopsis. Plant Physiology,
in press
Kaiser BN, SR Rawat, Siddiqi MY, Masle J, Glass AD 2002.
Functional analysis of an Arabidopsis t-DNA "knock-out"
of the high-affinity NH4+ transporter AtAMT1;1. Plant Physiology,
130: 1263-1275.
Masle J. 2002 Root impedance and plant performance-
Physiology, Genetic determinants. In: Plant Roots, The Hidden
Half (3rd edition) Y. Waisel, A. Eshel, U. Kafkafi eds, Marcel
Dekker, Inc. Publ, NewYork, 807-819.
Buer S, Masle J, Wasteneys GO. 2001 Growth conditions
modulate root-wave phenotypes in Arabidopsis thaliana. Plant and
Cell Physiology, 41:1164-1170.
Masle J. 2000. The effects of elevated [CO2]
on cell division rates, growth patterns and blade anatomy in young
wheat plants are modulated by factors related to leaf position,
vernalisation and genotype. Plant Physiology, 122:1399-1415.
Masle J. 1999. Root impedance: sensing, signalling
and physiological effects. In: Plant Responses to Environmental
Stresses: From Phytohormones to genome Reorganization. H.R. Lerner
ed., M. Dekker, Inc., New York Publ., Chapter 22, pp 476-495.
Masle J. 1998. Growth and stomatal responses
of wheat seedlings to spatial heterogeneity of mechanical resistance
to root penetration in wheat. Case of bi-layered soils. Journal
of Experimental Botany, 49:1245-1257.
Beemster, GTS, Masle, J, Williamson, RW and Farquhar,
GD 1996. Effects of soil resistance to root penetration
on leaf expansion. Journal of Experimental Botany, 47, 1663-1678.
Masle J, Badger MR, Hudson GS. 1993. Effects
of ambient CO2 concentration on growth and nitrogen use in tobacco
(Nicotiana tabacum) plants transformed with an antisense gene
to the small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase.
Plant Physiology, 103, 1075-1088.
Masle, J 1992. Will plant performance on soils
prone to drought or with high mechanical impedance to root penetration
be improved under elevated atmospheric carbon dioxide? Australian
Journal of Botany 40, 491-500.
Masle, J and Farquhar, GD 1988. Effects of soil
strength on the relation of water use efficiency and growth to
carbon isotope discrimination in wheat seedlings. Plant Physiology 86, 32-38.
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