In our lab, we are interested to understand the general process of cell separation in plants; and in particular how the abscission and dehiscence processes are regulated. Our model systems are Arabidopsis thaliana and Brassica napus. We are producing transgenic plants with the aim to understand and manipulate these processes. This work has both inherent scientific interest and commercial significance to the agricultural and horticultural industries. The approach we have adopted involves the study of cell wall hydrolases genes such as Polygalacturonase.
In December, 2000 the completed sequence of Arabidopsis thaliana was anounced to the international comunity. We are using this information to group all the putative polygalacturonase (PG) genes of this plant using the data of the sequencing released from this project ( Fig.1). So far we have identified that the PG gene family can be grouped into 5 different subfamilies. Our first task is to try to elucidate the function of at least one member of each subfamily by fusing the promoters of each representative gene to GUS.
We have shown that
there are specific and different PG genes that are expressed during dehiscence
and abscission. However we have shown that dehiscence of both pods and
anthers may be regulated by similar mechanisms to abscission by fusing
the promoters of such genes to GUS. Moreover the abscission of some
plant organs may also be under the same controlling system. Differential
display strategy is a poweful tool that we used in the lab and we are currently
studying other genes that may contribute to these processes and have isolated
a gene encoding a response regulator that is up-regulated specifically
at the junction between the seed and the funiculus. Studies are underway
to determine the signalling events that regulate the abscission and dehiscence
processes in plants.
REFERENCES
Roberts, J.A., Whitelaw CA, Gonzalez-Carranza ZH and McManus MT (2000) Cell separation processes in plants - Models, mechanisms and manipulation. Annals of Botany 86211-223.FOR MORE INFORMATION ABOUT OUR RESEARCH GROUP PLEASE GO TO THE WEB PAGE ADDRESS:Ruperti, B., Whitelaw, C.A. and Roberts, J.A. (1999) Isolation and expression of anallergen-like mRNA from ethylene-treated Sambucus nigra leaflet abscission zones. Journal of ExperimentalBotany 50 733-734.
Whitelaw, C.A., Paul, W., Jenkins, E.S., Taylor, V.M. and Roberts, J.A. (1999) A mRNAencoding a response regulator protein from Brassica napus is up-regulated during pod development. Journal of Experimental Botany 50 335-341.
Jenkins, E.S., Paul, W., Craze, M., Whitelaw, C.A., Weigand, A. And Roberts, J.A.(1999)Dehiscence-related expression of an
Arabidopsis thaliana gene encoding a polygalacturonase in transgenic plants of Brassica napus. Plant Cell and Environment 22 159-167.Gonzalez-Carranza, Z.H., Lozoya-Gloria, E. and Roberts, J.A. (1998). Recent developmentsin abscission: shedding light on the shedding
process. Trends in Plant Science 3 10-14.