Department of Biology, Lund University, Kontaktvägen 13, Lund, 223 62, Sweden.
Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, SciLifeLab, Umeå University, Umeå, Sweden.
BMC Microbiol. 2024 Nov 18;24(1):481. doi: 10.1186/s12866-024-03625-6.
SepIVA has been reported to be an essential septation factor in Mycolicibacterium smegmatis and Mycobacterium tuberculosis. It is a coiled-coil protein with similarity to DivIVA, a protein necessary for polar growth in members of the phylum Actinomycetota. Orthologues of SepIVA are broadly distributed among actinomycetes, including in Streptomyces spp.
To clarify the role of SepIVA and its potential involvement in cell division in streptomycetes, we generated sepIVA deletion mutants in Streptomyces venezuelae and found that sepIVA is dispensable for growth, cell division and sporulation. Further, mNeonGreen-SepIVA fusion protein did not localize at division septa, and we found no evidence of involvement of SepIVA in cell division. Instead, mNeonGreen-SepIVA was accumulated at the tips of growing vegetative hyphae in ways reminiscent of the apical localization of polarisome components like DivIVA. Bacterial two-hybrid system analyses revealed an interaction between SepIVA and DivIVA. The results indicate that SepIVA is associated with polar growth. However, no phenotypic effects of sepIVA deletion could be detected, and no evidence was observed of redundancy with the other DivIVA-like coiled-coil proteins Scy and FilP that are also associated with apical growth in streptomycetes.
We conclude that S. venezuelae SepIVA, in contrast to the situation in mycobacteria, is dispensable for growth and viability. The results suggest that it is associated with polar growth rather than septum formation.
SepIVA 已被报道为分枝杆菌属和结核分枝杆菌中必不可少的分隔因子。它是一种与 DivIVA 相似的卷曲螺旋蛋白，DivIVA 是放线菌门成员中极性生长所必需的蛋白质。SepIVA 的同源物广泛分布于放线菌中，包括链霉菌属。
为了阐明 SepIVA 的作用及其在链霉菌中潜在的细胞分裂参与，我们在委内瑞拉链霉菌中生成了 sepIVA 缺失突变体，发现 sepIVA 对于生长、细胞分裂和孢子形成不是必需的。此外，mNeonGreen-SepIVA 融合蛋白不在分裂隔膜处定位，并且我们没有发现 SepIVA 参与细胞分裂的证据。相反，mNeonGreen-SepIVA 以类似于 DivIVA 等极体成分的顶端定位方式积累在生长营养菌丝的顶端。细菌双杂交系统分析显示 SepIVA 和 DivIVA 之间存在相互作用。结果表明 SepIVA 与极性生长有关。然而，无法检测到 sepIVA 缺失的表型效应，也没有观察到与其他与链霉菌中顶端生长相关的类似 DivIVA 的卷曲螺旋蛋白 Scy 和 FilP 的冗余。
我们得出结论，与分枝杆菌的情况相比，委内瑞拉链霉菌中的 SepIVA 对于生长和生存不是必需的。结果表明它与极性生长有关，而不是隔膜形成。
