Bilateral BBSRC-FAPESP: Cellular and regulatory basis for early plant organ growth

A central problem in Biology is to understand how genes cause organs to grow to a specific shape and size. Plants are convenient to address this question because their overall growth results primarily from the increase in cell numbers and increase in the size of individual cells (cell movement and "pruning" by cell death do not need to be considered). In addition, understanding organ growth in plants offers a clear path to practical use through the rational manipulation of crop growth and yield.

A major bottleneck for understanding plant growth, however, is that although we know several genes that control the overall size and shape of organs, we do not understand what processes these genes control within cells (such as cell division or increase in cell mass) to result in a net effect on the total size and shape of organs. We aim to answer this question, by studying the early stages of floral organ development in the model species, Arabidopsis.

Unprecedented opportunities to address the question above arise from two recent developments. One is the establishment of methods that allow quantitative, 3D analysis of cell geometry and cell division in growing organs. Using these methods, the UK partner in this project has recently found that a key regulator of organ growth, called JAGGED (JAG), has an unanticipated role in co-ordinating cell volume with cell division in developing organs. The second is the development of techniques for detection of all genes controlled by a given regulatory gene, at well-defined stages of organ formation - this can reveal the repertoire of cellular functions that are controlled by a regulatory gene. Our Brazilian/Dutch partners have been developing these methods and applying them to understand the role of genes that control floral organ development.

Taking advantage of the complementary expertise, resources and biological interest of the UK and Brazilian/Dutch partners, we will extend both approaches to a key set of genes that control plant organ growth: JAGGED (JAG), AINTEGUMENTA (ANT) and CIN-TCP genes. We will test whether the co-ordination between cell size and cell division is a key feature of targeted by these genes at the early stages of organ growth. We will also test whether these genes target specific steps in cell division and clarify how the activities of these regulatory genes are combined during organ growth. Finally, we will identify the sets of genes controlled by JAG and CIN-TCP genes in the early stages of organ development - this will show to what extent the function of these genes overlap, and reveal the key cellular functions targeted by these genes to determine how the organs grow.

One of the current priorities in developmental biology is to develop computer models that can simulate and predict the way organs and organisms grow. Addressing the questions in this proposal will be essential for connecting these models with molecular mechanisms that can be controlled experimentally. Ultimately, this knowledge will allow rational modification of plant organ growth, which has an obvious impact on crop performance. In addition to addressing a fundamental biological question with strategic relevance, our work will establish new and mutually beneficial long-term scientific links between UK and Brazilian institutions.

To understand how the activity of regulatory genes within cells is translated into the shape and size of plant organs, we aim to reveal what growth-limiting cellular processes (e.g. cell cycle control, cytoplasmic growth, cell expansion) are targeted by regulatory genes that control plant organ growth. For this, we will take advantage of two recent developments. First, the establishment of methods that combine detection of newly synthesized DNA with quantitative analysis of cell geometry in 3D images of developing organs. Using these methods, the UK applicant has revealed an unanticipated role for the regulatory gene JAGGED (JAG) in co-ordinating cell volume with cell division in organ primordia. Second, the application of ChIP-seq on developmentally synchronised floral organs. The Brazilian applicant and Dutch collaborators have been developing these methods to understand the role of CIN-TCP genes in floral organ growth. We will combine the complementary expertise, resources and biological interest of the UK and Brazilian/Dutch partners to study the function of a key set of growth regulatory genes: JAGGED (JAG), AINTEGUMENTA (ANT) and CIN-TCP genes. We will test whether coupling of cell size and cell division is a key feature of primordium growth that is targeted by multiple regulatory genes. We will also test whether these genes target particular steps in cell division and clarify the genetic interactions between JAG, ANT and CIN-TCPs in the control of cell growth and division in developing organs. Finally, we will use ChIP on synchronised organ primordia to identify the sets of genes directly controlled by JAG and CIN-TCPs in the early stages of organ development.

In addition to addressing a fundamental question with long-term impact through the rational manipulation of crop growth and yield, our work will establish mutually beneficial scientific links between the UK and Brazil.

This project will benefit five main non-academic beneficiaries, in the following ways:

1. Breeders will benefit from knowledge that will facilitate the selection of candidate genes for improving crop growth and yield by conventional or transgenic approaches. The expected time frame for this beneficial impact will be 5-10 years after the start of the project.

2. Agricultural businesses will benefit from our work indirectly, through future use of the resources and knowledge made available to academic peers and to breeders. The most obvious potential benefit will be crop varieties with increased yield through changes in developmental constraints on growth. The channels to these beneficiaries will be breeders, as mentioned above, and licensing of patented knowledge through PBL Technologies (http://www.pbltechnology.com/). The time frame for this type of impact is expected to be 10-20 years.

3. Industry: depending on the career path of the person working on the project, the industrial sector may also benefit from personnel with unique training. This will include theoretical and technical knowledge ranging from molecular genetics to advanced biological imaging and image analysis, communication skills including the clarity and rigour required to write papers and talk at scientific meetings, and a network of contacts spanning academia and breeders (3-4 years).

4. The general public will benefit from interacting with researchers working in areas of public concern, such as food security and genetic modification. The channels for interaction with the public include the Teacher-Scientist Network (http://www.tsn.org.uk/) and presentations at the Friends of John Innes Society (http://www.jic.ac.uk/corporate/friends/index.htm) (3-4 years).

5. BBSRC will benefit because the project is directly relevant to the research priority Systems Biology. In addition, the project will establish concrete links between leading scientific institutions in Brazil and the UK; further development of these links is likely to open new opportunities in the BBSRC priority areas of bioenergy and food security (3-10 years).