The transposition of a heat-activated retrotransposon ONSEN resulted in changes in the hypocotyl elongation.

Abstract

In our study, we aimed to identify new mutants resulting from ONSEN transposition in Arabidopsis thaliana by subjecting nrpd1 mutants to heat stress. We isolated a mutant with a significantly elongated hypocotyl, named "Long hypocotyl in ONSEN inserted line 1" (HYO1). This phenotype was heritable, with progeny consistently displaying longer hypocotyls than the wild type. Genetic analysis revealed that this trait was due to a single recessive mutation. Further mapping and sequencing identified the insertion of ONSEN in the HY2 gene, a crucial regulator of hypocotyl elongation. The insertion disrupted HY2 transcription, as confirmed by quantitative PCR, leading to the observed phenotype. To assess the influence of the nrpd1 background, we generated lines backcrossed twice to wild-type Col-0, and the results were consistent with those observed in the original mutant lines. Furthermore, we examined the effect of HY2 and HYO1 mutations on flowering time by analyzing the expression levels of FT. The hyo1 mutant exhibited earlier flowering compared to both the wild type and nrpd1 mutants, with increased FT expression levels. This research underscores the significant impact of ONSEN transposition on gene function and phenotypic variation in Arabidopsis thaliana, providing new insights into the mutagenic potential of transposons and their role in shaping plant traits.