Functional Diversity of A-Type RING Ligases (ATL) Genes: Insights into the Crucial Roles of E3 Ubiquitin Ligases in Plant Biology

Abstract E3 ubiquitin ligases are vital components of the ubiquitin–proteasome system (UPS), responsible for maintaining protein balance and controlling cellular functions. E3 ligases target specific proteins for degradation or modify their activities through ubiquitin attachment. One prominent E3 ligase family is the ATL family, which comprises 100 members in Arabidopsis thaliana and has significantly expanded in plant genomes. All ATLs share a common domain architecture, featuring a transmembrane domain at the amino-terminal region, a distinct RING-H2 finger domain, and the GLD motif. The RING domain facilitates interactions between E3 ligases, E2-conjugating enzymes, and target proteins, enabling the transfer of ubiquitin molecules. The amino-terminal and carboxy-terminal regions introduce sequence diversity and potentially mediate interactions with other components that assist in UPS function or target recognition. ATLs had been classified within groups, each group encompasses specific ATLs with defined roles in various biological processes. For example, group C-ATLs are implicated in drought tolerance, flower development, phosphate homeostasis, and immune signaling. G-ATLs are associated with carbon/nitrogen stress, immune signaling, salt stress, ABA responses, cadmium tolerance, and sugar-mediated plant growth. A-ATLs participate in early elicitor-response, salt and drought responses, and flowering time regulation. Lastly, D-ATLs are involved in the regulation of programmed cell death. This review let perceive ATLs as a cohesive group of E3 ligases, shedding light on their functional diversifity and redundancy, specifically examining their participation in diverse biological processes, explore their evolutionary history shaped by gene duplication events, and appraise their interactions with key proteins and targets of ubiquitination. This comprehensive overview aims to offer insights into the role of ATLs in plant adaptation, defense mechanisms, and stress tolerance, while also underlying molecular and evolutionary mechanisms and regulatory networks that govern these processes.