Phenotype Analysis And Map-based Cloning Of Dwarf Mutant Gad5 In Maize

The gibberellins(GAs)hormones act throughout the life cycle of plants,influencing seed germination,stem elongation,flower induction,anther development,and seed and pericarp growth.Maize is an important food crops,feed sources,food ingredients and industrial raw materials and energy plants.With the sequence completion of the maize genome,more and more mutants were found and related genes were cloned and commented.gad5(GA Associated Dwarf 5)is formed by natural mutation which we discovered in the experiment,and it has the same heredity background with B73 inbred line.gad5 shows late of seed germinates,dwarf,short of internodes,small leaves,rounded leaf edges,late development of pistil and stamen,and infertility or abortion of pistil and stamen.The phenotypes of gad5 can inherit stably after backcrossed with B73 to purify its genetic background.The height of plant and leaves of gad5 can restore to the wide-type phenotype by applying a certain concentration of exogenous GA3,but when applying brassinosteroid(BR),the phenotypes can’t restore.So we conjecture that GAD5 is related with GA.By measuring the content of GAs in WT and gad5 through the method of enzyme-linked immunosorbent assays(ELISA),we found that the content of GAs in gad5 is less than that in WT,which furtherly suggests that the phenotype of gad5 is resulted in the lower content of GAs.The F2 exhibits separated phenotypes such as dwarf,short of internodes,small leaves,and rounded leaf edges after crossed with another maize inbred line Mo17.Genetic analysis of F2 showed that phenotype of gad5 is controlled by recessive single gene.Ather then,we initiate the work of map-based cloning of GAD5.We obtained 34 pairs of co-dominant markers by the method of bulked segregant analysis(BSA)screening of 384 pairs of maize polymorphic markers in primary mapping.The rate of exchange in co-dominant marker4E8(p-umc1212)on chromosome 9 is lowest,16.49%,by measuring the exchange rate.Therefore,we locate the GAD5 nearby 4E8(p-umc1212).Next we obtained another 11 co-dominant markers from MaizeGDB or developing SSR markers by ourselves to precisely map.We furthermore located GAD5 in the range of about 25 M of 9.03-9.04 bin on chromosome 9 by measuring the exchange rate and analyzing the trends.Above all,gad5 is formed by natural mutation,this mutant shows late of seed germinates,dwarf,short of internodes,small leaves,rounded leaf edges,late development of pistil and stamen,and infertility or abortion of pistil and stamen.It can make the mutant restore to wild-type phenotype by applying a certain concentration of exogenous GA3.GAs content in gad5 is less thanthat of WT by GAs content measured.Genetic analysis showed thatphenotypeof gad5 is controlled by recessive single gene.By map-based cloning technique,we located GAD5 in the range of about 25 M of 9.03-9.04 bin on chromosome 9.Studies about maize dwarf mechanism are a few and one main reason is the related mutants are only a few.The discovery of gad5 and the acquisition of GAD5 in the following work will help us elucidate the mechanism about the plant type and dwarf of maize.If it can be used to applications,it will greatly promote the development of the corn industry to facilitate the management and make corn harvesting.