Map-based Cloning And Fuctional Analysis Of Short Root Mutant 2-18 M-1 In Arabidopsisthaliana

The roots is important underground organ for high plants,which not only make plant fixed in the soil but also provides plant with water and mineral nutrition,and can respond to the changes of internal or external condition and make corresponding adjustment in plant growth and development,make plants to better adapt to the environment.Plant roots stem from root stem cells which locat in root stem cell niche.Root Stem Cell Niche?RSCN?consists of quiescent center?QC?and root stem cells.The cell to cell signaling between the QC and surrounding stem cells plays a vital role in maintaining stem cell identity.Hencecomplete structure and function of the stability of RSCN is required for normal root development.We screened an EMS?ethylmethane sulfonate?-treated seed library and obtained a short root mutant named 2-18 m-1.We performed the phenotypic analysis and map-based cloning analysis on mutant 2-18 m-1,the major results are presented as follows:1.Mutant 2-18 m-1 shows remarkable short primary root,shorten root meristem and reduced root meristem cells,and abnormally arranged starch grains in root cap cells;increased branch,late flowering and reduced fertility.These results indicate that themutation2-18 m-1 affects both the rootand aerial organ development.2.The expression of a QC-specific marker gene and Cyclin B1;1 is suppressed in mutant 2-18 m-1Via GUS histochemical assay,we found that the expression of QC-specific marker QC25 was reduced slightly in the mutant 2-18 m-1,the cell division marker Cyclin B1;1was also suppressed,suggesting that the maintenance of the root stem cell niche,and the division activity of root meristem may be affected in the mutant.3.The primary root of2-18 m-1 is less sensitivev to auxin and brassinosteroidat low concentrations,illustrate that mutation in 2-18 m-1 affects auxin and brassinosteroid-mediated root growth and development.4.Identified a point mutation in At GAPC2 through map-based cloningtechniqueGenetic analysis shows the 2-18 m-1 is a recessive mutant of a single gene.Through rough mapping,we found the mutation site of 2-18 m-1 being located around T20H2 on the chromosome 1.The fine mappingwas used to identify the mutation site being between T28K15 and F14L17,the genetic distance is about 206kb.Finally through gene prediction and sequencing,we fo und that a point mutationoccurred in At GAPC2,encoding a cytoplasmic glyceraldehyde-3-phosphate dehydrogenase,and the 229^{t h} base of C convertsinto T at the gene coding region,resulting in the substitution of proline by serine at77^th amino acid residue of the protein.In summary,the mutation in At GAPC2 leads to the defects of root growth,therefore,At GAPC2 may play an important role in the regulation of roots development.