An ACCUMULATION AND REPLICATION OF CHLOROPLASTS 5 gene mutation confers light green peel in cucumber

The peel color of fruit is an important commercial trait in cucumber, but the underlying molecular basis is largely unknown. A mutant showing light green exocarp was discovered from ethyl methane sulfonate (EMS) mutagenized cucumber line 406 with dark green exocarp. Genetic analysis showed the mutant phenotype is conferred by a single recessive gene, here designated as lgp (light green peel). By re-sequencing of bulked segregants, we identified the candidate gene Csa7G051430 encoding ACCUMULATION AND REPLICATION OF CHLOROPLASTS 5 (ARC5) that plays a vital role in chloroplast division in Arabidopsis. A single nucleotide polymorphism (SNP) causing amino acid alteration in the conserved GTPase domain of Csa7G051430 showed co-segregation with the altered phenotype. Furthermore, the transient RNA interference of this gene resulted in reduced number and enlarged size of chloroplasts, which were also observed in the lgp mutant. This evidence supports that the non-synonymous SNP in Csa7G051430 is the causative mutation for the light green peel. This study provides a new allele for cucumber breeding for light green fruits and additional resource for the study of chloroplast development.