Understanding how organisms regulate size is one of the most fascinating open questions in biology. The aim of the AMAIZE project is to unravel how growth of maize leaves is controlled. Maize leaf development offers great opportunities to study the dynamics of growth regulatory networks, essentially because leaf development is a linear system with cell division at the leaf basis followed by cell expansion and maturation. Furthermore, the growth zone is relatively large allowing easy access of tissues at different positions. Four different perturbations of maize leaf size will be analyzed with cellular resolution: wild-type plants and plants having larger leaves (as a consequence of GA20OX1 overexpression), both grown under either well-watered or mild drought conditions. Firstly, a 3D cellular map of the growth zone of the fourth leaf will be made. RNA-seq of three different tissues (adaxial and abaxial epidermis; mesophyll) obtained by laser dissection with an interval of 2.5 mm along the growth zone will allow for the analysis of the transcriptome with high resolution. Additionally, the composition of fifty selected growth regulatory protein complexes and DNA targets of transcription factors will be determined with an interval of 5 mm along the growth zone. Computational methods will be used to construct comprehensive integrative maps of the cellular and molecular processes occurring along the growth zone. Finally, selected regulatory nodes of the growth regulatory networks will be further functionally analyzed using a transactivation system in maize.
AMAIZE opens up new perspectives for the identification of optimal growth regulatory networks that can be selected for by advanced breeding or for which more robust variants (e.g. reduced susceptibility to drought) can be obtained through genetic engineering. The ability to improve the growth of maize and in analogy other cereals could have a high impact in providing food security.