Coordination of Cell Division and Differentiation 387
(Konishi and Sugiyama 2006). Cell proliferation in cultured calli is also af-
fected. RPD1 seems to be a plant-specific protein containing a winged-helix
fold similar to that present in the DNA binding domain of the E2F family
members, although the molecular basis for its function is not known.
3
Future Prospects
The last 5–10 years have witnessed an unprecedented advance in our under-
standing of cell proliferation control. The mechanism of action of individual
genes controlling different aspects of cell cycle is being elucidated. Their in-
tegration with developmental processes is also beginning to be understood.
These studies should definitely continue until comprehensive information of
each gene impinging on cell proliferation is available. However, we must face,
at least, two major challenges. One is to integrate the functional relationships
of different cell cycle regulators into common pathways. Another is the iden-
tification and understanding of the very complex transcriptional networks
that regulate cell proliferation and its coordination with development. The
availability of an increasing amount of plant lines with identified alterations
of individual genes affecting cell proliferation control in combination with
molecular, genetic and genomic tools should promote the next qualitative ad-
vance in the years to come.
References
Ahn JW, Kim M, Lim JH, Kim GT, Pai HS (2004) Phytocalpain controls the proliferation
and differentiation fates of cells in plant organ development. Plant J 38:969–981
Autran D, Jonak C, Belcram K, Beemster GT, Kronenberger J, Grandjean O, Inze D, Traas J
(2002) Cell numbers and leaf development inArabidopsis: a functional analysis of the
STRUWWELPETER gene. EMBO J 21:6036–6049
Blilou I, Frugier F, Folmer S, Serralbo O, Willemsen V, Wolkenfelt H, Eloy NB, Ferreira PC,
Weisbeek P, Scheres B (2002) TheArabidopsisHOBBIT gene encodes a CDC27 ho-
molog that links the plant cell cycle to progression of celldifferentiation. Genes Dev
16:2566–2575
Boniotti MB, Gutierrez C (2001) A cell-cycle-regulated kinase activity phosphorylates
plant retinoblastoma protein and contains, inArabidopsis, aCDKA/cyclin D complex.
Plant J 28:341–350
Boudolf V, Vlieghe K, Beemster GT, Magyar Z, Torres Acosta JA, Maes S, Van Der
Schueren E, Inze D, De Veylder L (2004a) The plant-specific cyclin-dependent kinase
CDKB1;1 and transcription factor E2Fa-DPa control the balance of mitotically dividing
and endoreduplicating cells inArabidopsis. Plant Cell 16:2683–2692
Boudolf V, Barroco R, Engler Jde A, Verkest A, Beeckman T, Naudts M, Inze D, De Veyl-
der L (2004b) B1-type cyclin-dependent kinases are essential for the formation of
stomatal complexes inArabidopsisthaliana. Plant Cell 16:945–955