Novel allele elh of the UBP14 gene affects plant organ size via cell expansion in Arabidopsis thaliana

Plant organ size control is an essential process of plant growth and development. The regulation of plant organ size involves a complicated network of genetic, molecular interactions, as well as the interplay of environmental factors. Here, we report a temperature-sensitive hypocotyl elongation EMS-generated mutant, hereby referred to as elongated hypocotyl under high-temperature (elh). The elongated hypocotyl phenotype was prominent when the elh seedlings were grown at high temperature, 28°C, but not under the growth temperature of 21°C. We observed significantly larger organ sizes in elh plants, including cotyledons, petals and seeds. In elh plants, the cell sizes in cotyledons and petals were significantly larger than wild type. By measuring the cell density and organ area of cotyledons, petals and mature dissected embryos, we found no differences in total cell numbers in any organ indicating that cell expansion rather than cell proliferation was perturbed in elh. elh plants produced leaves at a slower rate than wild type plants, suggesting that perturbing the balance between cell division and cell expansion is linked to the developmental rate at which leaves are produced.