New Tools for an Old Problem

Somatic and gametophytic embryogenesis are two examples of induced plant cell totipotency, where embryos develop from vegetative or gametophytic tissues, rather than from the zygote after fertilisation. These two types of in vitro embryogenesis form the basis for a number of plant breeding and biotechnology applications, including clonal propagation, doubled-haploid production and regeneration after transformation, but also offer good model systems for understanding how plant cells are reprogrammed to follow a new developmental pathway. The classical tissue culture approach used to overcome recalcitrance for in vitro regeneration in crops is to identify empirically the explant and culture parameters that contribute to efficient production systems. Almost all of the major breakthroughs in plant tissue culture have been achieved in this way, and although successful, this approach is often time consuming and inefficient, as only a few parameters can be tested at one time. A molecular-genetic approach is often used to identify the molecular pathways driving plant cell totipotency in model plant systems, but can be confounded by genetic redundancy, lethality, or pleiotropy.

Our lab is using a third approach, chemical screening, to overcome recalcitrance for in vitro embryogenesis in crops, and to better understand the mechanistic basis for induced totipotency. In this approach, individual compounds from commercial targeted and non-targeted compound libraries are screened for their ability to enhance embryogenesis, while keeping the tissue culture conditions constant. I will highlight the general concepts behind chemical screening and demonstate how we have used this approach to identify competence factors for gametophytic and somatic embryogenesis.