| Although plant growth is an important topic, the regulation of genes involved in growth is poorly understood. To contribute to current information about plant growth regulation, an early tuberization cDNA library from Solanum tuberosum L., expected to contain genes involved in cell proliferation, was screened for members of developmental regulatory gene families. The two objectives of this study were to isolate genes that might be involved in plant growth regulation, and to characterize the RNA accumulation patterns of these genes to gain insight into their function. The AAA-protein superfamily ATPase POTATP1 and the homeobox gene POTH1 were isolated to accomplish the first of these objectives. To accomplish the second objective, in situ hybridization analysis was performed on various organs of the potato plant with the homeobox gene POTH1 and the previously identified MADS-box gene POTM1.; POTH1 was shown to be a class I homeobox gene which differed substantially in both sequence and transcript accumulation pattern from other genes of its class. Its RNA accumulation pattern is widespread, including actively growing cells from both determinate and indeterminate, differentiated and undifferentiated tissues. Similarly, POTM1 transcript accumulation patterns are more widespread than those of other genes in the SQUA-like class of MADS-box genes, including both vegetative and reproductive tissues. POTM1 was expressed in inflorescent and floral meristems, in petal, stamen, and carpel primordia, and later in developing stamens and carpel interiors. Like POTH1 transcripts, POTM1 mRNA was shown to accumulate in vegetative shoot apical meristems, leafprimordia, and in actively growing cells of new leaves, leaflets, and stem vascular tissue. The common theme uniting these two genes is that both are preferentially expressed at the RNA level in actively growing cells of both indeterminate and differentiated tissue, indicating that POTH1 and POTM1 may be involved in regulating aspects of cell growth independent of differentiation level and determinacy status. These genes are good candidates for further study in both applied and basic research. |
