Fine Mapping And Characterization Of DNL2 And AB-1, Two Genes Involving In Plant Growth And Development In Rice

The rice EMS-derived dwarf and narrow leaf mutant 2 (dnl2) is isolated after EMS treatment on rice variety Zhonghuall. By using linkage analysis and fine mapping, we have located the chromosome region responsible for this abnormality. Further, phenotypic, physiological, and biochemical traits of this mutant were evaluated. On the other hand, we have also obtained rice leaf rolling mutant ab-1, which is selected after EMS treatment on rice varietyZhonghuall. We have examined the phenotypic, physiological, and biochemical characteristics of this mutant. In addition, protein-protein interaction and CRISPR/cas edited gene assay were also performed. The results of this study were summarized below:The dnl2-plant is dwarfed in stature, forms narrow leaves and its vegetative tissue at maturity is brittle. Its dwarfness was shown to be due to its foreshortened intemodes, resulting from a reduced size of the internode parenchyma cells. Its narrow leaf trait was attributed to a compromised ability to form vascular bundles, and the brittleness of its vegetative tissue at maturity results from reduced crude fiber content and a thin cortical layer. Transcription profiling indicated that a number of cell division/expansion-associated and crude fiber synthesis-related genes were down-regulated in the mutant. Physiological assay revealed that the responsive to the application of either gibberellin or the brassinosteroid brassinolide was no different between dnl2 and its wild type. A genetic analysis revealed that the mutant phenotype is under monogenic control, and the gene responsible was mapped to a 50.10 kb genomic region on the long arm of chromosome 10. And this region was shown to harbor ten open reading frames. Although transcription profiling of these genes indicated that three were differentially transcribed in the mutant, there was no sequence polymorphism in the coding sequence between the mutant’s and the wild type’s alleles. These results are crucial to understand the molecular mechanism of DNL2, which is required to direct the normal growth and development of rice plant.The ab-1 developed several morphological defects, characterized by a low grain yield and a manifested delay in senescence. Map-based cloning has revealed a transcription factor KAN1 as the causal factor of this abnormal phenotype. The rolling phenotype emerged together with altered bulliform cells in adaxial side of ab-1’s leaves. Transgenic lines derived from the CRISPR/cas-edited genes showed a functional overlap between AB-1 and its family members KAN2 and KAN3 in rice, consistent with that reported in Arabidopsis. The ab-1 has exhibited abnormal sensitivity to 1-naphthaleneacetic acid (NAA), indole-3-Acetic acid (IAA), and a compromised response to gibberellic acid (GA3), owing to its disrupted phytohormone content, especially GA3. AB-1 has interacted with ARF3 as described in Arabidopsis, with ARF15 as predicted in rice and with ARF7 whose ortholog SIARF7 mediate cross-talk between IAA and GA in Solanum licopersicum. The AB-1 is supposed to be implicated in GA signaling, maybe in cooperation with ARF7. The AB-1IARFs proteins complexes were absolutely needed for leaf polarity determination in rice.