Gene Mapping Of White Vein Reverse Mutants In Arabidopsis Thaliana

Variegation mutants have patches of differing colors on the leaves.There is a subset of variegation mutants which display color difference between veins and leaves is called reticulate mutants.Most of the reticulate mutants are caused by nuclear genes that affect chloroplast development and primary metabolism.These mutants are valuable resource in studying the development of mesophyll cells and plant vascular cells as well as the development and function of chloroplasts.var5 is a newly discovered Arabidopsis reticulate mutant characterized with white veins and green leaves.The gene responsible for the mutation was MGT10 encoding a magnesium transporter protein.MGT10 is localized in the envelope of chloroplasts and is highly expressed in vascular cells.In the MGT10 deficient mutant,the veins appeared yellowish-white,the thylakoid grana increased,and the chloroplast magnesium ion content increased.However,the mechanism of MGT10 affecting the abnormal vein color is still unknown.We found the mgt10 mutant in an EMS mutant screen of Arabidopsis plants.In order to explore the genes function with MGT10,we performed a suppressor mutation screen with the white vein mutant.Some recovery mutants were screened.The veins in the 147 mutant and the 60 mutant turned completely green.Gene analysis confirmed that the two mutants are respectively caused by a single nuclear gene mutation with recessive phenotype.The restored mutant was crossed with mgt10,and the F2 plants with the green vein phenotype were pooled for genome sequencing.The mutant gene was mapped with Mutmap method,and a candidate gene PKP1 in which a site mutation causes the early termination of PKP1 synthesis was found in the 147 restored mutant.When the wild-type PKP1 gene was transferred into 147 restored plants,the white vein phenotype appeared in the transgenic plants suggesting that the mutation of PKP1 suppressed the white vein phenotype of mgt10.We determined that PKP1 was localized in the chloroplast.Bioinformatic analysis showed that the promoter of PKP1 contained many cis-acting elements related to light response.Some candidate genes in the 60 restored mutant were identified by genome sequencing analysis.Functional verification of these genes has been carried out.Our research will find new genes functioning with MGT10 to control the function of chloroplast in the vascular cells.