Fine Mapping and Candidate Gene Analysis of the Leaf-Color Gene <i>ygl-1</i> in Maize

<div><p>A novel yellow-green leaf mutant <i>yellow-green leaf-1</i> (<i>ygl-1</i>) was isolated in self-pollinated progenies from the cross of maize inbred lines Ye478 and Yuanwu02. The mutant spontaneously showed yellow-green character throughout the lifespan. Meanwhile, the mutant reduced contents of chlorophyll and Car, arrested chloroplast development and lowered the capacity of photosynthesis compared with the wild-type Lx7226. Genetic analysis revealed that the mutant phenotype was controlled by a recessive nuclear gene. The <i>ygl-1</i> locus was initially mapped to an interval of about 0.86 Mb in bin 1.01 on the short arm of chromosome 1 using 231 yellow-green leaf individuals of an F₂ segregating population from <i>ygl-1</i>/Lx7226. Utilizing four new polymorphic SSR markers, the <i>ygl-1</i> locus was narrowed down to a region of about 48 kb using 2930 and 2247 individuals of F₂ and F₃ mapping populations, respectively. Among the three predicted genes annotated within this 48 kb region, <i>GRMZM2G007441</i>, which was predicted to encode a cpSRP43 protein, had a 1-bp nucleotide deletion in the coding region of <i>ygl-1</i> resulting in a frame shift mutation. Semi-quantitative RT-PCR analysis revealed that <i>YGL-1</i> was constitutively expressed in all tested tissues and its expression level was not significantly affected in the <i>ygl-1</i> mutant from early to mature stages, while light intensity regulated its expression both in the <i>ygl-1</i> mutant and wild type seedlings. Furthermore, the mRNA levels of some genes involved in chloroplast development were affected in the six-week old <i>ygl-1</i> plants. These findings suggested that <i>YGL-1</i> plays an important role in chloroplast development of maize.</p>