Specialization of the Golden2-like regulatory pathway during land plant evolution.

* The development of photosynthetic competence is a key requirement for all land plants and many aquatic algae. Previous work has demonstrated that a pair of Golden2-like (GLK) transcription factors regulates chloroplast development in diverse land plants, in that recessive glk1;glk2 mutants are pale green and fail to accumulate components of the light-harvesting machinery. To determine the extent to which the GLK pathway has diverged in land plants, we compared GLK gene function in the flowering plant Arabidopsis thaliana and the moss Physcomitrella patens.

AtMCP1b, a chloroplast-localised metacaspase, is induced in vascular tissue after wounding or pathogen infection.

cDNA corresponding to the Arabidopsis type I metacaspase AtMCP1b was isolated from plants infected with Pseudomonas syringae. A positive correlation between AtMCP1b expression and cell death was observed in the presence of staurosporine, a protein kinase inhibitor that induces programmed cell death. The tissue localisation of an AtMCP1b promoter-GUS fusion was observed in the vascular tissue of transgenic plants.