Hormone Signaling

Signal Interaction

Genomics

Ethylene-Auxin interactions in Arabidopsis roots

Using classical physiological approaches and utilizing a large collection of ethylene and auxin mutants available, we showed that auxin is required for the inhibitory effects of ethylene on growth of roots but not of hypocotyls of dark-grown Arabidopsis seedlings. The analysis of ethylene and auxin responses at the cellular level in a selected subset of these mutants provided the basic framework for a mechanist model of the interaction between these two important hormones. Root-specific whole-genome expression profiling studies not only supported the model proposed, but also suggested existence of several levels of interactions between ethylene and auxin.

Characterization of wei2 and wei7

   Cloning and characterization of the two root-specific ethylene insensitive mutants, wei2 and wei7, has unveiled a new point of interaction between ethylene responses and auxin biosynthesis. We have shown that these genes are required for an ethylene-mediated increase in auxin levels in Arabidopsis root tips. Analysis of the expression patterns of WEI2 and WEI7 indicates that these two genes are transcriptionally regulated be ethylene and are co-expressed in the same cells. We have also shown that mutations in either one of these two genes suppress the auxin overproduction defects of sur1 and sur2 both in seedlings and adults. Remarkably, the double mutants wei2 sur1 and wei7 sur1 are viable and produce seeds whereas sur1 is completely sterile.

Characterization of wei8, tar1, and tar2

The analysis of a root-specific ethylene insensitive mutant wei8 has uncovered a novel genetic element involved in a key step of auxin biosynthesis. Mutant alleles of paralogous genes TAR1 and TAR2 have been identified allowing for the generation of the triple wei8 tar1 tar2 mutants. Characterization of the triple mutant combinations confirms the crucial role of this small gene family in the control of auxin production in plants. An in-depth study of these genes will be critical to establishing not only how, but also when and where, auxin is synthesized. 

Characterization of ead1 and peo1

Identification and characterization of ead1 and peo1 mutants clearly indicates that EAD1 and PEO1 function is required for normal ethylene and auxin responses. The potential role of these proteins in the control of protein translation of putative targets is currently being tested.

Protocol setup for BAC tagging using recombineering approaches

We have shown that tags can be precisely and easily fused to a gene of choice present in a large artificial chromosome by employing newly developed highly efficient homologous recombination systems in E. coli. These recent technical advances are making it possible to easily manipulate and modify large DNA molecules such as BACs without the need for restriction enzymes and classical cloning techniques. Currently, we are adapting and optimizing existing recombineering techniques to enable Arabidopsis gene tagging at a high-throughput scale.