Translational research: maize leaf and ear development
The maize leaf offers great potential to study the dynamics in growth networks
Complementary to the Arabidopsis leaf, we use the maize leaf as a tool to study growth regulatory responses under control and mild drought conditions.
The maize leaf offers great potential to study the dynamics in growth networks because of the linear organization of the growth zone and its size. When the maize leaf is growing, dividing expanding and mature cells are organized sequentially. At the base of the maize leaf, in the division zone (DZ), cells are actively dividing. Approximately 14 mm from the base of the fourth leaf cells stop dividing and start expanding. This marks the transition zone (TZ1) that is followed by the expansion zone (EZ). In addition, the size of the distinct zones allows to sample each zone separately, obtaining enrichment of dividing, transitioning and expanding cells in sufficient amounts for many genome wide technologies (Nelissen et al., 2013). Unraveling the molecular processes in the distinct zones of the growing maize leaf offers opportunities to study the dynamics of growth networks.
Capturing the dynamics of cellular and molecular processes in the maize leaf growth
We are continuously striving to increase our insights in the cellular processes within the maize leaf (Nelissen et al., 2013; Voorend et al., 2014) and to optimize maize plant phenotyping. At a molecular level, we apply detailed transcriptome (Candaele et al., 2014), (targeted) metabolome (Nelissen et al., 2012) and interactome (Nelissen et al., 2015) analyses to study the molecular mechanisms that define the interplay between cell division and cell expansion, and thus determine organ growth. The combinatory approach of cellular and molecular analysis allowed to identify distinct ways to regulate the dynamics in growth. Hormone and transcript measurements along the growth zone, combined with the cellular analysis of mutants and overexpression lines of enzymes in the GA biosynthetic pathway, showed that the transition from cell division to cell expansion (TZ1) was characterized by a local accumulation of GA (Nelissen et al., 2012). Tandem affinity purification on samples enriched for dividing and expanding tissues revealed that growth zone dependent protein-protein interactions were crucial to determine TZ1 (Nelissen et al., 2015). Besides the information from our molecular studies in maize, we also take advantage of the plethora of knowledge affecting growth obtained in Arabidopsis thaliana (intrinsic yield genes, stress tolerance genes and the molecular yield networks) and assess its translatability to maize (Nelissen et al., 2014). Therefore, we combine the phenotyping of lines perturbing the function of selected growth regulators with the genetic and molecular interactions around these nodes to build growth regulatory networks. We also aim to understand the relevance of our greenhouse based research for agriculture by performing field trials with growth phenotypes (Nelissen et al., 2014).
Besides biotech research, we also study the variation in leaf growth parameters by using different inbreds, recombinant inbred lines and hybrids (Dell’Acqua et al., 2015).
The maize leaf of the future
Up to now, we gathered a substantial toolbox to perform maize biotech research, varying from efficient transformation, optimized growth conditions, kinematic analysis, bio-informatics and computational tools, genome-wide technologies to field trials and automated systems to phenotype the plants. Our aim is to continue to optimize and develop technologies to gain a better understanding of the processes driving growth and to expand our knowledge on growth regulatory networks. Furthermore, we are evaluating how the growth regulatory mechanisms operating in the leaf function in controlling the maize ear growth.
People involved: Hilde Nelissen (project leader), Joke Baute, Michiel Bontinck, Jolien De Block, Kirin Demuynck, Kim Feys, Katrien Maleux, Stien Mertens, Xiaohuan Sun, Tom Van Hautegem, Lennart Verbraeken, Liesbeth Vercruyssen, Charlot Versteele, Astrid Welvaert, Nathalie Wuyts
Visiting scientist: Hironori Takasaki
Nelissen, H., Rymen, B., Jikumaru, Y., Demuynck, K., Van Lijsebettens, M., Kamiya, Y., Inzé, D., and Beemster, Gerrit T.S. (2012). A local maximum in gibberellin levels regulates maize leaf growth by spatial control of cell division. Current Biology 22, 1183-1187.
Nelissen, H., Rymen, B., Coppens, F., Dhondt, S., Fiorani, F., and Beemster, G.S. (2013). Kinematic analysis of cell division in leaves of mono- and dicotyledonous species: A basis for understanding growth and developing refined molecular sampling strategies. In Plant Organogenesis (Methods in Molecular Biology Vol. 959), I. De Smet (ed.), New York, Humana Press, pp. 247-264.
Nelissen, H., Moloney, M. and Inzé, D. (2014). Translational research: from pot to plot. Plant Biotechnol J. 12(3):277-85.
Candaele, J., Demuynck, K., Mosoti, D., Beemster, G. T., Inzé, D. and Nelissen, H. (2014). Differential methylation during maize leaf growth targets developmentally regulated genes. Plant Physiol. 164(3):1350-64.
Voorend W, Lootens P, Nelissen H, Roldán-Ruiz I, Inzé D, Muylle H. (2014). LEAF-E: a tool to analyze grass leaf growth using function fitting. Plant Methods. 10(1):37.
Nelissen H, Eeckhout D, Demuynck K, Persiau G, Walton A, van Bel M, Vervoort M, Candaele J, De Block J, Aesaert S, Van Lijsebettens M, Goormachtig S, Vandepoele K, Van Leene J, Muszynski M, Gevaert K, Inzé D, De Jaeger G. (2015). Dynamic Changes in ANGUSTIFOLIA3 Complex Composition Reveal a Growth Regulatory Mechanism in the Maize Leaf. Plant Cell doi 10.1105/tpc.15.00269
Dell’Acqua, M., Gatti, D. M., Pea, G., Cattonaro, F., Coppens, F., Magris, G., Hlaing, A. L., Aung, H. H., Nelissen, H., Baute, J., Frascaroli, E., Churchill, G. A., Inzé, D., Morgante, M., and Pè, M. E. (2015). Genetic properties of the MAGIC maize population: a new platform for high definition QTL mapping in Zea mays. Genome Biology