Required for the cellularization of the syncytial blastoderm embryo. Involved in the localization of the actin filaments just prior to and during plasma membrane invagination. Sry-alpha together with nullo and bnk may provide auxiliary functions, by acting both to stabilize a large and dynamic microfilament structure and regulate its functions (By similarity). Inner membrane-associated and cytoplasmic. Colocalizes with the structural transitions in the microfilament network during cellularization (By similarity). Blastoderm.