Dalekin is a novel plant hormone that is made in the plant roots; it moves through the plant to signal the perception of drought and salt stress. These stresses are known to repress growth, and dalekin does this by repressing WUS expression (which is necessary for shoot stem cells that allow for plant growth). Because dalekin is over-produced in bps1 mutants, the loss-of-function bps1 mutant is believed to normally function to regulate the synthesis of dalekin. The phenotype that results from the excess of dalekin in bps1 mutants is that both shoots and roots are highly abnormal. However, a cold-sensitive suppressed line was isolated after bps1 was crossed to a different accession (Apost-1). These plants, which we call Red4A bps1, produce normal-looking shoots and roots that are somewhat short and highly branched when grown at warm temperatures. Because drought stress is an urgent problem, my project is to identify additional genes that function through dalekin signaling.
To identify genes that function in dalekin synthesis or response, I am characterizing suppressor mutants. Mutagenesis was carried out using Red4A bps1 seeds, and the mutagenized seeds were grown at warm temperatures to collect self-pollinated seedlings. The resulting self-pollinated seeds were then grown at the restrictive temperature (16˚C), and suppressors (called RT lines) were identified because they, but not the parental Red4A bps1, were able to flower and set seeds. My goal is to identify one of the genes that, when mutated, allowed bps1 suppression. Identifying suppressor genes will help us understand the dalekin signaling and biosynthesis pathway.
Because mutagenesis leads to many mutations across the genome, the RT lines were then backcrossed to Red4A bps1, F1 seeds were grown and allowed to self-pollinate, and F2 seeds recovered. The F2 seeds are homozygous for bps1 but segregate for the RT suppressor. I am currently characterizing the phenotypes and segregation ratios of the