Map-Based Cloning Of A New Albino Gene In Rice

Albino mutants are ideal materials for studying chlorophyll biosynthesis and metabolic regulationof chloroplast development in plant photosynthetic system. Due to easily distinguishing on theirphenotype of leaf color, it is also considered as a kind of genetic markers in practical breeding programto simplify the distinguishing on false hybrid. In this study, one rice albino mutant, which couldgradually return to green color in four-leaf seedling period, was used. After preliminarily studying on itsphenotype and physiology, we isolated the mutant gene based on the method of map-based cloning.Following are our results:(1) The mutant showed a severe bleaching leaf color at beginning, from the fourth new leaf on, itreturned to normal green color. Temperature-sensitive experiments displayed the phenotype is inducedby low temperature; the severer albino phenotype and slower growth rate are closely associated withlower temperature, as well as chlorophyll content in mutant. However, no significant difference wasobserved at30℃growth condition.(2) Using200F2individuals of cross-combination "Jin23B×02428", the target gene was roughly linkedand marked by the primers on the long arm of chromosome3, and further finely mapped to32.7kbinterval delimited by InDel markers of YS44and YS45. Sequencing analysis revealed that a single-basedeletion presenting on the first open reading frame of gene LOC_Os03g15033, which putatively lead tothe pre–mature termination of the amino acid translation. The identity of candidate gene was confirmedby the genetic complementary experiment.(3) Through bioinformatics analysis, the LOC_Os03g15033which has four copies in rice was foundhighly homologous with EEE58716. It belongs to the DUF3353superfamily which has unknownfunction.(4) Fluorescence quantitative expression analysis showed that the base deletion of mutant resulted thereduction of LOC_Os03g15033expression level related to that of wild type. Moreover, in mutant thegene HEMA1increased its expression level and genes CHLD, PORA and CHIH decreased theirexpression amount, indicating LOC_Os03g15033playing a role between the first step and the ninth stepof the chlorophyll biosynthetic pathway：the first step,L-glutamyl-tRNA is reduced to glutamyl theacyloxy-tRNA-1-semialdehyde by glutamyl-tRNA reductase;and the ninth step,The protoporphyrin IXgenerates magnesium protoporphyrin Ⅸ by the magnesium chelatase.