Cell cycle control and plant development. Annual Plant Reviews, Volume 32
Cell cycle control and plant development. Annual Plant Reviews, Volume 32D. Inzé ed. 2007. Oxford: Wiley-Blackwell.
£99.50 (hardback). 364 pp.
There is an increasing awareness amongst the plant cell cycle community that cell cycle genes interface with growth and development. Increasingly, snippets of information have shown that growth and development can be affected by over-expression of cell cycle genes, although how this interface operates and how cell cycle genes talk to developmental genes remains shrouded in mystery. In this one consolidated volume, a group of internationally renowned plant cell cyclists have turned their thoughts to the problem. This is both welcome and timely. Not surprisingly, several authors tackle the cellular and organismic theories of development in relation to cell number and cell size. In my view, some authors have become somewhat entrenched in the intricacies of each theory whilst others refreshingly conclude that current data cannot support either theory alone (e.g. Larry Fowke's chapter). So, does the cell drive the organism or vice versa? Does it matter in efforts to unravel regulation of plant growth and development? I don't think so, but read on.
The book comprises 16 chapters. Space limitations do not permit a detailed critique of each one, but here instead is a very brief chapter-by-chapter tour. Denes Dudits et al. review plant cyclin-dependent kinase families; so many members per group, a typical plant cell cycle trait! Jim Murray et al. provide an elegant overview of D-type cyclins, whilst Larry Fowke et al. provide a very interesting account of cyclin-dependent kinase inhibitors (known as CKIs in animal cell cycle parlance) and their effects on development. Somewhat confusingly, plant orthologues are known as interactors with cyclin-dependent kinases (the ICKS) or Kip-related proteins (KRPs). They have profound effects on plant development. Pascal Genshik et al. brings us nicely up to date with how the plant cell eradicates unwanted cell cycle proteins. It was refreshing to read about the plant Anaphase Promotion Complex, which is at the heart of so much of the degradative processes; bravo mon ami! Akie Shimomoto and Masaaki Umeda give a superb overview of phoshoregulation of CDKs, whilst Crisanto Guiterez et al. bring us up to date with E2F-DP transcription factors. This complex is a critical driver of cells into DNA replication (S-phase of the cell cycle). Wilhelm Gruissem follows with an account of retinoblastoma- (Rb) related proteins in plants. Whilst E2F complexes are the ‘go’, Rb(s) is the stop for entry into S-phase. Tom Beeckman et al. consider auxin regulation of lateral root initiation and were able to tie in a lot of cell cycle activity to auxin control of root branching. Andrew Fleming covers cell cycle control in leaf development; he tends to conclude that it is the growing leaf that drives where and when cell division occurs during leaf development. In this regard, I am always intrigued by R. F. Lyndons's observations of increased cell division in an incipient primordium occurring about 3–4 d before the primordium begins to bulge. I have always concluded that this tiny cluster of cell divisions is the start of a leaf primordium. Lieven De Veylder et al. focus on the ‘endocyle’. In the cell cycle, cells can complete DNA replication and by-pass mitosis. If these cells continue on this iterative route, the nuclear DNA amount increases and cells get bigger. Plant cells can exhibit much endoreduplication. The late Walter Nagl's exposition of this process in the suspensor of Phaseolus coccineus always springs to my mind although, curiously, Jack Van't Hof uncovered many plants cells and many plant species that don't do it. Lieven's very thorough treatment of this process is followed by Larkins et al. who review the endocycles during trichome development. Much of the information therein was relatively new to me; an enjoyable read. Christian Chevalier provides a very nice overview of fruit development and also focuses on endoreduplication, a good match with the two previous chapters. Paolo Sabelli et al. review endosperm development; for me, one of the most fascinating cells cycle stories in higher plants. It continues to remain an intriguing enigma why the progenitor of the endosperm, triploid nucleus/cell can divide faster than diploid cells of the zygote! There then follows a chapter by Peter John, whose chapters are always worth waiting for. This one is no exception. He tackles cellular and organismal theories head-on and concludes (correctly I believe) that cell division might not necessarily drive plant growth but it is indispensable for continuing growth. Bravely, he also tackles an enigma that won't go away: why do cytokinins (which by definition stimulate cell division) promote shoot growth but repress root growth (as judged by cytokinin-induced repression of lateral root primordium formation and the size of the root apical meristem)? I am not sure that he has unravelled the mystery. Just as well really; it keeps all of us busy! The final chapter is by Christine Granier, Sarah Cookson, Francois Tardieu and Bertrand Muller. The Montpellier group review the cell cycle and environmental stress. This group has been at the forefront of very elegant measurements of organ growth. I think we will continue to argue about the rights and wrongs of kinematic and chemical methods for measuring cell cycles (vive la différence) but it is interesting how their detailed analyses provide evidence of cell division as a driver of organ growth in some cases and as an accompaniment to growth in others. Plants are sessile and extraordinary biochemical machines. Their ability to switch processes on and off almost instantly must surely reconcile us to merge holistic and cellular theories of development and how cell division impacts on growth. I congratulate Dirk Inzé for assembling a book that so expertly illustrates the complex entwinement of cell division with growth and development in plants. I enjoyed reading each chapter. Possibly there ought to be more cross-referencing but the volume will be an essential accompaniment to anyone working on the plant cell cycle. The market for the volume is consistently the same for all specialist books, i.e. university libraries and a copy in the lab. For me the volume is full of excellent information, carefully and thoughtfully presented. To those who buy/read this volume – enjoy! Of course, it's not quite as good as the very recently published Eukaryote Cell Cycle (eds Bryant and Francis) but there again, self-praise is no recommendation.
E-mail francisd{at}cardiff.ac.uk
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