Coordination of N 2 -fixing cell specialization and patterning in filamentous cyanobacteria by a uniquely structured σ factor - Xi Hu; Xujiao Liu; Yali Wang; Ke Liu; Hong Gao; Geqian Zhu; Shuai Wang; Xiantao Fang; Hong Sun; Fang Zhou; Shuiling Ji; Congzhao Zhou; et al. (Proceedings of the National Academy of Sciences, 2026)