Identification of a Chlorophyll-Deficient Mutant in Maize Associated with Exogenous Vector Insertion

TL;DR

A chlorophyll-deficient maize mutant was identified, showing altered chloroplast development linked to a transgenic vector insertion.

Contribution

The study identifies a new maize mutant with chlorophyll deficiency caused by an exogenous vector insertion.

Findings

The mutant phenotype is inherited in a Mendelian 3:1 ratio, controlled by a single nuclear locus.

Mutant cells lack normally developed chloroplasts, and chloroplast gene expression is impaired.

The mutant phenotype is associated with the entire inserted vector, not a point mutation or deletion.

Abstract

Leaf color mutants are commonly characterized by altered chlorophyll content and aberrant chloroplast development, making them valuable models for investigating photosynthetic mechanisms and chloroplast biogenesis. In this study, an albino mutant was isolated from a population of transgenic maize breeding lines. Genetic analysis indicated that the mutant phenotype is inherited in a Mendelian manner and is controlled by a single nuclear locus. This was supported by a χ2 test performed on the T2 generation, which confirmed a segregation ratio consistent with 3:1 (176:68, χ2 = 1.07 < χ20.05 = 3.84, p > 0.05). Microscopic examination revealed the absence of normally developed chloroplasts in mutant cells. Further expression analysis of chloroplast genes via Northern blotting and quantitative real-time PCR (qRT-PCR) suggested that the mutation impairs the regulation of plastid-encoded polymerase (PEP)-dependent chloroplast gene expression. Notably, PCR-based co-segregation analysis indicated that the mutant phenotype is associated with the entire inserted vector sequence, rather than a point mutation or a small genomic deletion. In conclusion, this paper reports the isolation and phenotypic characterization of an etiolated mutant from a transgenic maize breeding population, including comparative ultrastructural analysis of chloroplasts, co-segregation validation, and chloroplast gene expression profiling. These results enhance our understanding of the physiological and molecular mechanisms underlying chlorophyll-deficient mutations in plants.

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