A New Allele of the SPIKE1 Locus Reveals Distinct Regulation of Trichome and Pavement Cell Development and Plant Growth

The single-celled trichomes of have long served as an elegant model for elucidating the mechanisms of cell differentiation and morphogenesis due to their unique growth patterns. To identify new components in the genetic network that governs trichome development, we carried out exhaustive screens for additional Arabidopsis mutants with altered trichome morphology. Here, we report one mutant, ( ), with a reduced trichome branching phenotype. After positional cloning, a point mutation in the ( ) gene was identified in . Further genetic complementation experiments confirmed that is a new allele of , so was renamed as according to the literatures. and two other mutant alleles, covering a spectrum of phenotypic severity, highlighted the distinct responses of developmental programs to different mutations. Although null mutants are lethal and show defects in plant stature, trichome and epidermal pavement cell development, only trichome branching is affected in . Surprisingly, we found that is involved in the positioning of nuclei in the trichome cells. Lastly, through double mutant analysis, we found the coordinated regulation of trichome branching between and two other trichome branching regulators, ( ) and ( ). might serve for the precise positioning of trichome nuclei, while and contribute to the formation of branch points through governing the cMTs dynamics. In summary, this study presented a fully viable new mutant allele of and shed new light on the regulation of trichome branching and other developmental processes by .