The SpoVA membrane complex is required for dipicolinic acid import during sporulation and export during germination

Abstract

In response to starvation, endospore-forming bacteria differentiate into stress-resistant spores that can remain dormant for years yet rapidly germinate and resume growth in response to nutrients. The small molecule dipicolinic acid (DPA) plays a central role in both the stress resistance of the dormant spore and its exit from dormancy during germination. The spoVA locus is required for DPA import during sporulation and has been implicated in its export during germination, but the molecular bases are unclear. Here, we define the minimal set of proteins encoded in the Bacillus subtilis spoVA operon required for DPA import and demonstrate that these proteins form a membrane complex. Structural modeling of these components combined with mutagenesis and in vivo analysis reveal that the C and Eb subunits form a membrane channel, while the D subunit functions as a cytoplasmic plug. We show that point mutations that impair the interactions between D and the C–Eb membrane complex reduce the efficiency of DPA import during sporulation and reciprocally accelerate DPA release during germination. Our data support a model in which DPA transport into spores involves cycles of unplugging and then replugging the C–Eb membrane channel, while nutrient detection during germination triggers DPA release by unplugging it.

Dipicolinic acid enhances kiwifruit resistance to Botrytis cinerea by promoting phenolics accumulation

“…It was also indicated that some of DPA's antioxidant effects were caused by the formation of a chelation complex with copper. That previous report, together with the high occurrence of DPA in Bacillus species, 41,42 suggested that DPA could be one of the metabolites involved in the antioxidant effects produced by Bacillus species 43–45 . For this reason, the antioxidant activity of DPA was screened in this study to reveal new insights into the metabolites that may be involved in Bacillus ‐induced defense responses.…”

Single-spore germination analyses reveal that calcium released duringClostridioides difficilegermination functions in a feed-forward loop

“…DpaAB encodes the enzyme complex that synthesizes CaDPA (Fig 1A, (35,36)), while SpoVV and SpoVAC are critical in B. subtilis for transporting CaDPA across the outer and then inner forespore membranes, respectively (37,38) (Fig 1A). SpoVV function was first established in B. subtilis (37), whereas SpoVAC has been shown to transport CaDPA into the spore core in several spore-formers, including C. difficile (32,35,(39)(40)(41)(42)(43). CD3298 may act as an accessory protein for the SpoVV or the SpoVAC transporter, although CD3298 lacks a signal sequence (( 23 difficile.…”

“…DpaAB is the enzymatic complex that synthesizes DPA, which complexes with Ca 2+ ions before it is transported across the outer (OM) and inner forespore membranes (IM). SpoVV is the putative CaDPA transporter in the OM (37), while SpoVAC is the CaDPA transporter located in the IM (43). CD3298 (orange circle) is a putative ATP-binding protein previously shown to be important for CaDPA transport in C. difficile (23), but it is unclear whether it associates with SpoVV or SpoVAC.…”

The underlying mechanism of bacterial spore germination: An update review

“…Although the profile of the germination process, especially physiological events, is relatively clear, signal transduction and the underlying mechanisms are obscure. Recently, the application of AlphaFold 2 to identify the spatial structure of GRs or Ca‐DPA channel proteins revealed their possible mode of action during germination (Amon et al., 2022; Artzi et al., 2021; Y. Gao, Barajas‐Ornelas, et al., 2022), and the finding that potassium ion release integrates germination signals sheds light on the mystery process of signal transduction following GRs activation (Kikuchi et al., 2022). Moreover, the occurrence of macromolecule synthesis during germination (Sinai & Ben‐Yehuda, 2016; Sinai et al., 2015; Zhou et al., 2022, 2019) and the proposed high correlation between ATP levels and spore germination capability (Rao et al., 2022) have been demonstrated, but these concepts are controversial (Boone & Driks, 2016; Korza et al., 2017, 2023, 2016; Swarge, Abhyankar, et al., 2020; Swarge, Nafid, et al., 2020).…”