A fasciclin-like arabinogalactan protein OsFLA8 is involved in Casparian strip formation and salt tolerance in rice.

FASCICLIN-LIKE ARABINOGALACTAN PROTEINs (FLAs), a subclass of plant arabinogalactan proteins (AGPs), play diverse roles in plant development, including pollen development, secondary cell wall regulation, and root and stem growth. However, the biological functions of the majority of FLA-encoded proteins in rice remain largely unexplored, particularly their roles in root development and cell wall formation. In this study, we identified OsFLA8, a member of the FLA family, as a critical component of Casparian strip (CS) formation and salt stress tolerance in rice. Subcellular localization and expression analysis revealed that OsFLA8 is a protein localized to both the endoplasmic reticulum and plasma membrane, with high expression levels in the elongation zone of rice roots. Knockout of OsFLA8 resulted in the defective CS formation with reduced lignin deposition in the endodermis, without significantly affecting suberin accumulation. And mutation of OsFLA8 increased sensitivity to salt stress and calcium treatment due to disrupted Na+ and Ca2+ homeostasis, compared to wild-type plants. Furthermore, we demonstrated that the transcription factor OsMYB36a directly regulates OsFLA8 expression by binding to its promoter. Our findings highlight the critical role of OsFLA8 in maintaining ion homeostasis and stress tolerance in rice, providing new insights into the regulatory network of CS formation and abiotic stress responses.