Phospholipid analogs and beyond: pleiotropic roles of betaine lipids in phycology, ecology, and biomedicine.

Betaine lipids (BLs) are a class of non-phosphorus glycerolipids widely found in microalgae, fungi, bacteria, mosses, and ferns. For decades, the central paradigm regarding the biological function of BLs has been their role in substituting for phospholipids under phosphate starvation-a crucial adaptive mechanism for survival in oligotrophic environments. However, accumulating evidence indicates that the functional diversity of BLs is far more extensive. Recent studies have demonstrated their distinct roles in fatty acid metabolism, adaptation to various environmental stresses, and ecological interactions such as symbiosis and predation. This review summarizes current insights into the pleiotropic roles of BLs in microalgal physiology and ecology, moving beyond their role as mere phospholipid surrogates. Furthermore, we highlight the recently discovered bioactive function of BL derivative in mammals.