| Finding / claim | Evidence type / method | Biological context (tissue / time) | Key details / quantitative info | Citation context ID(s) | Source URL and publication year |
|---|---|---|---|---|---|
| Soybean ENOD2 mRNA localizes mainly to the nodule inner cortex, also termed nodule parenchyma | In situ hybridization / autoradiography with antisense RNA probes | Mature soybean root nodules | Strong signal over inner cortex; little or no signal over outer cortex / vascular bundle; lower signal over endodermis and adjacent outer cortex | (pqac-00000000, pqac-00000001) | https://doi.org/10.1002/j.1460-2075.1990.tb08073.x (1990) |
| Soybean ENOD2 transcripts are also detected in cells surrounding the connecting vascular bundle between nodule and root | In situ hybridization | Mature soybean nodules; tissue around connecting vascular bundle | Signal present in inner cortex plus cells around the vascular strand linking nodule to root central cylinder | (pqac-00000000, pqac-00000003, pqac-00000008, pqac-00000009) | https://doi.org/10.1002/j.1460-2075.1990.tb08073.x (1990) |
| ENOD2 is expressed early during nodule development, before nitrogen fixation | Developmental staging plus in situ hybridization | Developing soybean nodules | Soybean ENOD2 messenger detectable by about day 6 after sowing / inoculation; by day 10 signal is strong in inner cortex and around vascular strand | (pqac-00000002, pqac-00000003, pqac-00000008, pqac-00000009) | https://doi.org/10.1002/j.1460-2075.1990.tb08073.x (1990) |
| ENOD2 expression is associated with differentiation of nodule inner cortical cells | Histology plus in situ hybridization | Early nodule primordia and developing nodules | Expression reported upon differentiation of nodule meristem into inner cortical cells, supporting a developmental marker role for parenchyma formation | (pqac-00000001, pqac-00000003) | https://doi.org/10.1002/j.1460-2075.1990.tb08073.x (1990) |
| Soybean ENOD2 encodes a proline-rich, likely hydroxyproline-rich cell-wall protein | cDNA sequence analysis and comparative protein inference | Protein-level functional inference for soybean nodulin-75 / NGm-75 | Protein described as very proline-rich and built largely from pentapeptide repeats containing two prolines; strongly resembles soybean cell-wall glycoproteins | (pqac-00000000, pqac-00000001, pqac-00000002) | https://doi.org/10.1002/j.1460-2075.1990.tb08073.x (1990) |
| A putative N-terminal signal peptide supports secretion of ENOD2 to the cell wall / apoplast | Sequence analysis / bioinformatic inference from soybean ENOD2 genes | Protein precursor architecture | Sequence analysis indicates a putative N-terminal signal peptide, consistent with a secreted hydroxyproline-rich cell-wall protein precursor | (pqac-00000003) | https://doi.org/10.1002/j.1460-2075.1990.tb08073.x (1990) |
| ENOD2 is induced in bacteria-free or “empty” nodules, indicating activation by early symbiotic signaling rather than infection alone | Comparative expression analysis in effective, ineffective, and empty nodules; cited developmental genetics evidence | Nodules elicited by certain Rhizobium / Bradyrhizobium strains and by Agrobacterium carrying nod genes | Supported as expression in empty nodules and after nod gene signaling; evidence is supportive but mainly summarized from primary studies rather than quantified in the excerpt | (pqac-00000002, pqac-00000005) | https://doi.org/10.1002/j.1460-2075.1990.tb08073.x (1990); https://doi.org/10.31274/rtd-180813-10838 (1998) |
| Proposed function is structural: ENOD2 likely contributes to specialized parenchyma morphology and possibly oxygen-diffusion barrier properties | Functional inference from localization plus protein class | Nodule parenchyma / inner cortex | Because ENOD2 is a putative cell-wall protein concentrated in inner cortex, authors propose it helps shape parenchyma morphology linked to the oxygen-diffusion barrier protecting nitrogenase | (pqac-00000000, pqac-00000001, pqac-00000003) | https://doi.org/10.1002/j.1460-2075.1990.tb08073.x (1990) |
| Later review-level synthesis suggests ENOD2 may not be strictly required for oxygen regulation, highlighting uncertainty in functional assignment | Literature synthesis / dissertation review | Legume nodules; family-level interpretation including soybean comparisons | Review summarizes evidence that ENOD2 is cell-wall associated and may influence structure, but notes some cited studies argue against a strict oxygen-regulation role | (pqac-00000004, pqac-00000007) | https://doi.org/10.31274/rtd-180813-10838 (1998) |
| A 2024 review links boron deficiency with impaired early nodulin protein biosynthesis, including ENOD2, and reduced soybean nodulation | Review article synthesis | Soybean nodulation under boron deficiency | Review states boron deficiency impairs nodulation in soybean due to impaired biosynthesis of early nodulin proteins such as ENOD2; this is a secondary-source claim and not ENOD2A-specific experimental proof | (pqac-00000004) | https://doi.org/10.3389/fpls.2024.1332459 (2024) |


*Table: This table compiles the main direct and indirect evidence for soybean ENOD2/early nodulin-75, emphasizing localization, developmental timing, protein-class inference, signaling context, and a recent boron-related update. It is useful for distinguishing experimentally supported findings from broader review-based interpretations.*