Red lettuce NAR and  green spontaneous mutants  GSL and GSL-DG
The lettuce line NAR was developed from cv. Annapolis via tissue culture selection for deep red color. NAR accumulates very high levels of anthocyanins and total phenolics. After multiple generations of line maintenance by self-pollination, a spontaneous green revertant, later named Green Super Lettuce (GSL), was detected among red NAR seedlings. GSL had light green leaves with irregular red sectors, indicating the phenotype was likely caused by an actively jumping DNA transposon and that the green phenotype was recessive. Metabolic analysis found that GSL almost entirely lacked anthocyanins, but it accumulated much higher levels of quercetin glycosides than NAR. Later, a spontaneous mutant was found among GSL seedlings after multiple generations of seed propagation. This plant had olive-green leaves with red sectors and segregated to three offspring phenotypes: a) GSL (light green, with red spots), b) GSL-Dark Green (GSL-DG, olive green with no red leaf sectors), and c) GSL-DG with red leaf sectors (GSL-DG(r)). This indicated that GSL-DG lettuce harbored a second allele of the gene causing the GSL phenotype. In this project, RNA-sequencing was conducted on RNA isolated from 3 NAR leaves, 3 GSL leaves and 3 GSL-DG leaves. The plants were grown under cool fluorescent lights expected to induce anthocyanin biosynthesis.