Investigating the developmental defects of rescued mpk3-/ mpk6- Arabidopsis plants [abstract]

Abstract

Mitogen Activated Protein Kinases (MAPKs) are signaling molecules involved in transducing extracellular signals into intracellular responses. Twenty MAPK genes have been identified in the fully sequenced Arabidopsis genome. To deduce the function of MPK3 and MPK6 (the two most closely related Arabidopsis MAPKs), we obtained the corresponding T-DNA single knockout mutants. Homozygous single mutants had no obvious phenotype. However, we failed to generate double mutants (mpk3-/-mpk6-/- ) and found these plants to be lethal in the early embryo stages. Normal embryogenesis starts with elongation of the zygote followed by cell division to form two cells of different sizes and different fates. However this asymmetric cell division is defective in the double mutants. We generated conditionally rescued double mutants by introducing a steroid (DEX) inducible MPK6 transgene. The resulting (MPK3-/-/MPK6-/-/DEX:MPK6+/+ ) seedlings, however, were abnormal and unable to develop. Their growth was extremely stunted, they had irregular leaf surfaces (stomata clustering) and had no real stem or roots. To understand the molecular mechanisms underlying this embryogenesis defect in the double mutant, we are using reporter genes and Affymetrix GeneChip analysis to investigate the involvement of plant hormones.