New Wine in an Old Bottle: Utilizing Chemical Genetics to Dissect Apical Hook Development

Abstract

The apical hook is formed by dicot seedlings to protect the tender shoot apical meristem during soil emergence. Regulated by many phytohormones, the apical hook has been taken as a model to study the crosstalk between individual signaling pathways. Over recent decades, the roles of different phytohormones and environmental signals in apical hook development have been illustrated. However, key regulators downstream of canonical hormone signaling have rarely been identified via classical genetics screening, possibly due to genetic redundancy and/or lethal mutation. Chemical genetics that utilize small molecules to perturb and elucidate biological processes could provide a complementary strategy to overcome the limitations in classical genetics. In this review, we summarize current progress in hormonal regulation of the apical hook, and previously reported chemical tools that could assist the understanding of this complex developmental process. We also provide insight into novel strategies for chemical screening and target identification, which could possibly lead to discoveries of new regulatory components in apical hook development, or unidentified signaling crosstalk that is overlooked by classical genetics screening.

Precise Regulation of the TAA1/TAR-YUCCA Auxin Biosynthesis Pathway in Plants

“…The use of small chemical inhibitors can complement classical genetics. These small molecules often competitively occupy the ligand binding pocket of the target enzymes and can be applied in discreet doses to give a wide range of effects [27][28][29]. To date, several auxin biosynthesis inhibitors have been found and widely used, including nalacin [30], NPA [31], and auxinole [32].…”

To curve for survival: Apical hook development

“…But, since the phytohormone signaling and cell growth regulatory mechanisms that have critical roles in apical hook development, such as auxin transport and signaling, usually participate in other plant growth processes as well, genetic modifications even using the transgenic‐free method may not be proper. To this end, the screening and subsequent optimization of small molecules that can be applied at more precise time windows during seed germination and early seedling establishment would be a more application‐potent direction (Aizezi et al, 2022).…”