Screening And Gene Mapping Of A Short-day-dependent Lesion Mimic Mutant Sdl In Arabidopsis

In this paper, a short-day-dependent lesion mimic mutant mutant (sdl), which develops lesions under short-day conditions(8hr light/16hr dark), was isolated from the populations of wild-type Arabidopsis thaliana (ecotype Columbia erecta) whose seeds were treated with Ethyl methane sulfonate(EMS).The sdl mutant, which spontaneously develops lesions on its leaves without pathogen attack and wrinkles irregularly, grows more slowly and is more dwarf than the wild-type plant under short-day conditions. Furthermore, the acrocarpous plant shows albino stems, wilting siliques and flower buds after bolting. However, those morphological change of sdl mutant never leads to the death of the whole plant.The sdl mutants were reciprocal crossed with Arabidopsis wild-type Col-0. All F₁ plants showed wild-type phenotype(without lesions). The phenotype segregation of mutant and the wild-type was observed in F₂ population. Chi-square test indicates that the segregation ratio is 3:1, which proves that it is a single recessive nuclear gene mutation. By comparing sdl mutant of this study with previously published Arabidopsis lesion mimic mutants, we find that it is a new mutant.To map sdl locus, homozygous sdl mutants(Columbia ecotype) were crossed with wild-type plants(Landsberg ecotype). Mapping populations, which is compsed of seedlings developing lesions under short-day conditions, were screened from the F₂ population. First-pass mapping with 24 molecular markers that well distributed in each of the five chromosomes of Arabidopsis indicates that the SDL gene is located on chromosome I and is tightly linked to molecular marker SGCSNP374. Then more genetic populations were employed and new molecular markers were designed. Further analysis shows the SDL gene has been mapped to a region of 180Kb located in BAC clone F25C20 and F12F1 between the molecular markers M3918 and M4102.