Abstract: The structure and function of a regulatory gene, SHORT-ROOT (SHR), is described. The SHR gene is expressed specifically in root progenitor tissues of embryos, and in roots and stems of seedlings and plants. SHR expression controls cell division of certain cell types in roots and affects the organization of root and stem tissues, and affects gravitropism of aerial structures. The invention relates to the SHR gene, SHR-like genes, SHR gene products, (including but not limited to transcriptional products such as mRNAs, antisense, and ribozyme molecules, and translational products such the SHR protein, polypeptides, peptides and fusion proteins related thereto), antibodies to SHR gene products, SHR promoters and regulatory regions and the use of the foregoing to improve agronomically valuable plants.

Abstract: An Arabidopsis thaliana double mutant ssl2 slr having a mutation in at least one base of the SSL2 genomic gene shown in SEQ ID NO: 3, obtained by: treating an Arabidopsis thaliana slr dominant mutant (FERM BP-8385), which has no lateral roots, with a mutagen; preparing plants of the next generation of the mutagen-treated slr dominant mutant; and selecting a plant that basically preserves phenotypes of the slr dominant mutant but has lateral roots from the plants of the next generation.