Genetic Analysis Of Sawtooth-like Leaf Mutant In Arabidopsis Thaliana

Abstract A mature leaf shows a polar structure with three dimensions and recentlythe research on leaf polarity formation becomes an attractive topic of study. Incurrent work, we discussed the mechanism controlling leaf serrate formation and thefunctions of chromosome structure on the leaf polarity formation through geneticanalysis of sawtooth-like leaf (sawl ) mutant in Arabidopsis. In our study, sawl shows pleimorphic phenotypes including sawtooth-like leaf andthe phenotypes were caused by a recessive single locus. The SAM phenotype of themutant suggested that the mutations produced in very early development stage. Wethen cloned the mutated gene based on mapping. DNA sequencing showed that a Gto T switching in the ORF of FASCIATA1 (FAS1) resulted in an ahead of scheduletranslation stop codon thus made the sawl a null mutant of FAS1 gene. We found thatthe expression of the adaxial identity gene of ASYMMETRIC LEAVES1 (AS1) wasdownregulated in sawl by using RT-PCR. Subsequently we observed a highfrequency of needle-like leaf in sawl as1-101 double mutant, indicating sawlstrengthened the phenotype of as1-101. Our research showed: the downregulated expression of AS1 was at least partiallyresponsible for the formation of serrate leaf in sawl. This supports a recentlyproposed model, which the juxtaposition of adaxial and abaxial cell fates is requiredfor blade outgrowth. In addition, as a subunit of CAF-1 (Chromatin AssemblyFactor-1), FAS1 stabilizes the chromosome structure directly and its null mutantincreased the frequency of needle-like leaf suggesting that expression of the factorspromoting radicalized leaf formation had been repressed by epigenetic mechanismin the process of evolution.