Plant growth is determined by small groups of cells called meristems. Meristems produce the leaves, branches and flowers of the plant. Knotted1-like homeobox (knox) genes are expressed in meristems and stems and are required for meristem function and leaf patterning. KNOX proteins are also sufficient for meristematic identity and are able to confer meristem fate on leaves if expressed inappropriately. KNOX proteins are members of the TALE class of transcription factors that are conserved in animals and plants. They function as biochemical partners with BEL1-like (BELL) proteins to bind DNA and thus regulate transcription. There are eight KNOX proteins and 13 BELL proteins in Arabidopsis. The proposed research will determining which KNOX protein interacts with which BELL protein and in what cell compartment and in what tissue. These experiments will be carried out in Arabidopsis. Biochemical experiments will also determine what genes are regulated by KNOX proteins in maize and rice by identifying the DNA which is bound by KNOX proteins and following transcription profiles. The third aim is to determine what are the regulatory sequences that keep knox genes from being expressed in leaves. A number of dominant mutants exist in maize that misexpress knox genes in leaves. Similar mutations are found in barley and snapdragon. These mutations all have rearrangements in intronic sequences, the part of the gene that does not code for protein. Molecular genetic experiments will determine what are the important sequences that keep knox genes from being expressed in leaves. The information gained from these experiments will provide an understanding of plant architecture and lead to improved crop yields. During the summer, a high school chemistry teacher from San Francisco will join the graduate students on the project to participate in the biochemistry experiments. In addition, the PI will bring genetics to the 7th grade of a rural middle school each spring to look at genetic ratios segregating on maize ears and isolate DNA.
