ARABIDOPSIS: A RICH HARVEST 10 YEARS AFTER COMPLETION OF THE GENOME SEQUENCE
Arabidopsis and primary photosynthetic metabolism – more than the icing on the cake
Mark Stitt*, John Lunn and Bjorn Usadel ¨ Max Planck Institute of Molecular Plant Physiology, Am Muhlenberg 1, D-14476 Potsdam-Golm, Germany ¨Received 25 November 2009; revised 3 January 2010; accepted 6 January 2010. * For correspondence (fax +49 331 567 8101; e-mail email@example.com).
SUMMARY Historically speaking, Arabidopsis was not the plant of choice for investigating photosynthesis, with physiologists and biochemists favouring other species such as Chlorella, spinach and pea. However, its inherent advantages for forwardgenetics rapidly led to its adoption for photosynthesis research. In the last ten years, the availability of the Arabidopsis genome sequence – still the gold-standard for plant genomes – and the rapid expansion of genetic and genomic resources have further increased its importance. Research in Arabidopsis has not only provided comprehensive information about the enzymes and other proteins involved inphotosynthesis, but has also allowed transcriptional responses, protein levels and compartmentation to be analysed at a global level for the ﬁrst time. Emerging technical and theoretical advances offer another leap forward in our understanding of post-translational regulation and the control of metabolism. To illustrate the impact of Arabidopsis, we provide a historical review of research in primaryphotosynthetic metabolism, highlighting the role of Arabidopsis in elucidation of the pathway of photorespiration and the regulation of RubisCO, as well as elucidation of the pathways of starch turnover and studies of the signiﬁcance of starch for plant growth. Keywords: photosynthesis, Arabidopsis thaliana, sucrose, starch, photorespiration.
INTRODUCTION Photosynthetic primary metabolismmight be regarded as a mature ﬁeld. It is covered in textbooks at length, and many readers probably dismiss it as ‘boring’ biochemistry, where the important questions were asked and answered long ago. In fact, photosynthesis research is undergoing a renaissance, driven by a renewed appreciation of the basic importance of crop yield. Arabidopsis has played a key role in elucidating the pathways andregulation of photosynthesis. As the knowledge base and experimental toolkit in Arabidopsis expanded, important problems that were previously intractable have become accessible. Many central questions could only be tackled in the last decade, following sequencing of the Arabidopsis genome and the advent of functional genomics. These advances provide an excellent starting point for systems analysis.Arabidopsis was not initially the plant of choice for investigating photosynthesis, at least from the point of view of physiologists or biochemists. Important experimental
ª 2010 The Authors Journal compilation ª 2010 Blackwell Publishing Ltd
systems for photosynthesis research in the past included the green alga Chlorella for elucidation of the C3 pathway (Calvin–Benson cycle) of CO2 ﬁxation,photosynthetic bacteria for structural studies, and spinach and pea, due to the ease with which intact functional thylakoids and chloroplasts could be prepared from their leaves, and the ready availability of large amounts of leaf material for biochemical work. Spinach, sunﬂower and other species with large ﬂat leaves were well suited for gas exchange measurements. Tobacco later rose to prominencedue to its ease of nuclear and plastid transformation. Discovery and elucidation of the C4 and crassulacean acid metabolism (CAM) pathways of photosynthesis were largely performed in C4 grasses (e.g. sugarcane, maize and Panicum spp.) and members of the Crassulaceae (e.g. Kalanchoe spp.). Neverthless, the power of Arabidopsis ¨ forward genetics quickly led to it becoming an important species in...