Genetically encoded betalain-based RUBY visual reporters: noninvasive monitoring of biological processes

Genetically encoded enzymatic and fluorescence-based reporters have become powerful tools to monitor and visualize diverse cellular processes. Despite their vast utility, some of these reporters require invasive analysis, while others need costly equipment and/or exogenous substrates. Recently, a new class of visual reporters have been developed based on the synthesis of betalains, which are either red or yellow pigments that produce outputs visible to the naked eye without the need for exogenous substrates. Since 2020, the betalain-based RUBY reporter has been used to visually track various cellular processes. Here, we explore the applications of RUBY in basic research and agriculture, discuss its limitations, and highlight its potential as an educational tool for teaching fundamental concepts in cell and molecular biology.