Edinburgh, Scotland, United Kingdom - TAIR

PHYTOCALPAIN as a key regulator of growth
in plants
Co-ordination of cell division and expansion between different cell types (such
as epidermis and mesophyll) is critical for the efficient functioning of plant organs,
and is likely to be effected by multiple interlinked mechanisms allowing
adaptation to both exogenous and endogenous cues. Here we show that DEK1
(also known as PHYTOCALPAIN), a unique plant-specific protein, plays a
fundamental role in regulating both cell division and cell expansion in Arabidopsis
organs. DEK1 contains a domain showing high homology to animal cysteine
proteases of the calpain family. Unlike animal calpains, DEK1 has a highly
extended N-terminal region containing numerous predicted trans-membrane
spans. In plant tissue, the DEK1 calpain domain is released from the full-length
protein by autocatalytic processing. Expression of the active calpain domain
alone is sufficient for full complementation of the early embryo lethality caused
by loss of DEK1 function. Thus, as reported in some animal systems, cleaved
calpain may represent the activated form of the protein. Although decreased
accumulation leads to severe epidermal abnormalities, phenotypes generated by
over-expression of the active calpain domain show that DEK1 it does not directly
regulate epidermal cell fate. Instead we hypothesise that aspects of growthco-ordination
which are critical for maintenance of epidermal integrity during
development are compromised by loss of DEK1 activity. Ongoing research into
understanding the mechanisms underlying DEK1–mediated growth control will
be discussed.
70
C19
Wednesday 16:30 - 17:00
Development
Kim Johnson1,2
Christine Faulkner2,3
Chris Jeffree3
Gwyneth Ingram3
1University of Edinburgh
UK
2John Innes Centre
Norwich
UK
3University of Edinburgh
UK