Preliminary Study On Mutation Type Of Waxy Gene In Landraces Of Waxy Maize From Southwest China

The glutinous endosperm of the waxy maize was controlled by a recessive mutation named waxy,which character was that starch of kernel endosperm was almost erythroamylose.The waxy maize,with many excellent characters,better quality,higher economy value,is the important raw material for food industry,textile,paper-making,micro brew and feedstuff.Through studied on mutations of waxy maize,overseas researchers had thought that because Ac/Ds,Spm/En transposon and retrotransposon had been inserted into flanking region,intron,exon of waxy gene,or waxy gene had deleted sequences,correct expression of waxy gene had been influenced,then prohibitted amylose synthesis.Germplasm resources of waxy maize in our country were extremely abundant,and most parts of germplasm resources were distributed in Southwest,which is the centre of genetic diversity of waxy maize.So it's extraordinary necessary to research the genetic mechanism of waxy phenotype of waxy maize from Southwest China,providing for information on conservation and utilization of germsplasm resources of waxy maize and breeding.In the study,waxy maize landraces from Southwest China(six samples),flint maize landraces from Southwest China(two samples),inbred line,huangzaosi,derived from tangsipintou that was representative germplasm from huanghuaihai area(one sample),American waxy maize(two samples)and Ameican common maize(there samples)were collected as experimental materials. Through sequencing coding region of waxy genes,sequnces,structural feature and genetic mechanism of waxy gene in landraces of waxy maize from Southwest were analyzed.And the following results are received:1.In the paper,among 6 waxy maize landraces from Southwest,we found that zaobainuo from Mengzi,Yunnan province,piantounuo from Zhenkang,Yunnan Province and changchongbainuo from Anlong,Guizhou Province all had a repeat insertion segment of 16bp in the ninth exon.It had not been reported about the mutation mode of waxy gene.Through comparing amino acid sequences,we discovered that amino acid sequences QHHAP that were coded by insertion sequences located in glycogen synthase domain.If the structural domain had been changed,it might have a bad effect on glycogen synthase,even lead to enzyme inactivation. Therefor,we could presume that the insertion sequences of 16bp in the ninth exon may be a sort of new mutation mode of waxy maize landraces from Southwest.2.Silunuo from Xishuangbanna,Yunnan Province had a series of original traits of maize, which was always collected as experimental material by many researchers.So we analyzd its sequence of coding region,and found that it had a deletion segment of 15bp in the tenth exon, and the location and length of deletion segment was as the same as the result discovered by Tian Mengliang(2008),which had studied 12 waxy maize landraces from Southwest,including zaobainuo,piantounuo and changchongbainuo.Amino acid sequences NKEAL that were coded by deletion sequences located in initiation region of Glycosyl transferases group 1 domain of Wx protein.If the domain had been changed,it might lead to enzyme inactivation directly.Therefor, we could presume that the deletion segment of 15bp may be one kind of major mutation mode of waxy maize landraces from Southwest.3.When analyzed the sequences of coding region of waxy gene for the 14 materials,we found that piantounuo has a mutation of AG to AT(1683bp-1684 bp)at the end of the second intron;and liuchengnuo has a mutation of GT to AT(3101bp-3102bp)at the beginning of the ninth intron.At present,there haven't been seen reports that waxy phenotype of waxy maize is caused by bases mutation which happened in the shearing location between exon and intron of waxy gene.Furthermore,K.M.Olsen & M.D.Purugganan(2002)found that,bases mutation that happened in the shearing site of 5′terminatio in the first intron of waxy rice is the essential condition of waxy phenotype of rice.Therefor,we could presume that bases mutation which happened in the shearing location may be a sort of new mutation mode of waxy maize landraces from Southwest.4.Comparing the intron sequences of waxy gene,we found that,2 flint maize landraces from Southwest and backbone inbred line huangzaosi had an insertion segment of 8bp length in the thirteen intron.Therefor,we could presume that,the insertion sequences of 8bp length in intron13 might be one of the symbols of difference between Chinese common maize and waxy maize landraces from Southwest.