CAUT lines: a novel resource for studies of cell autonomy in Arabidopsis

Suitability of two distinct approaches for the high-throughput study of the post-embryonic effects of embryo-lethal mutations in Arabidopsis

Several hundred genes are required for embryonic and gametophytic development in the model plant Arabidopsis thaliana, as inferred from the lethality of their mutations. Despite many of these genes are expressed throughout the plant life cycle, the corresponding mutants arrest at early stages, preventing the study of their post-embryonic functions by conventional methods. Clonal analysis represents an effective solution to this problem by uncovering the effects of embryo-lethal mutations in sectors of mutant cells within an otherwise normal adult plant. In this pilot study, we have evaluated the suitability of two sector induction methods for the large-scale study of the post-embryonic effects of embryo-lethal (emb) mutations in Arabidopsis. In line with the interests of our laboratory, we selected 24 emb mutations that damage genes that are expressed in wild-type vegetative leaves but whose effects on leaf development remain unknown. For the induction of mutant sectors in adult plants, we followed one approach based on the X-ray irradiation of 'cell autonomy' (CAUT) lines, and another based on the site-specific excision of transgenes mediated by Cre recombinase. We conclude that both methods are time-consuming and difficult to scale up, being better suited for the study of emb mutations on a case-by-case basis.

Uncovering the post-embryonic functions of gametophytic- and embryonic-lethal genes

An estimated 500-1 000 Arabidopsis (Arabidopsis thaliana) genes mutate to embryonic lethality. In addition, several hundred mutations have been identified that cause gametophytic lethality. Thus, a significant fraction of the ∼25,000 protein-coding genes in Arabidopsis are indispensable to the early stages of the diploid phase or to the haploid gametophytic phase. The expression patterns of many of these genes indicate that they also act later in development but, because the mutants die at such early stages, conventional methods limit the study of their roles in adult diploid plants. Here, we describe the toolset that allows researchers to assess the post-embryonic functions of plant genes for which only gametophytic- and embryonic-lethal alleles have been isolated.