## 5 Concluding Remarks  
_G. max_ exhibits notable gene duplication events, highlighting its potential as a compelling model species for studying the evolutionary dynamics of AsA synthesis. The higher number of AsA-encoding genes in this species compared to _Arabidopsis_ can be attributed to gene duplication events, mainly involving neo/subfunctionalization. Gene expression analyses suggested that the four proposed AsA biosynthesis pathways are actively functioning in _G. max_ and revealed a differential regulation of these pathways depending on the circumstances at different periods of the soybean's life cycle. The D-mannose/L-galactose pathway plays a predominant role in AsA biosynthesis. Nevertheless, the L-glucose, D-galacturonate, and Myo-inositol pathways also contribute to AsA synthesis dependent on tissues, developmental stages, and stress conditions. The expression data revealed that in developing tissues/organs, higher AsA mass fractions could be associated with the upregulation of genes from all four proposed pathways (except for Myo-inositol pathways in leaves). This was particularly observed in young leaves and germinating seeds. Under abiotic stresses, reduced AsA mass fractions were consistent with reduced key transcript levels of the D-mannose/L-galactose pathway; however, gene upregulation of alternative pathways of AsA biosynthesis indicates a fine regulation to maintain AsA levels availability for ROS scavenging activity. RNA-seq data of cultivars/genotypes with contrasting tolerance to biotic stresses also revealed potential stress resistance-linked genes (marked with asterisks in Figure 11). The genes _GMP_2a_ from D-mannose/L-galactose, GulLO_1f from the L-glucose pathway, and _MIOX_3a_ from the Myo-inositol pathway exhibited remarkable overexpression under stress conditions. Despite not being among the major sources of AsA, these analyses also demonstrated that germinating seeds, leaves, and roots of _G. max_contained adaptive fractions of AsA in dry masses. These findings together are promising for future experimental studies that aim to validate the highlighted candidate genes for their use in functional marker-assisted plant holobiont selection [72] or bioengineering strategies to improve plant stress resilience and plant resources for vitamin C.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/ijms26104678/s1](https://www.mdpi.com/article/10.3390/ijms26104678/s1)]([https://www.mdpi.com/article/10.3390/ijms26104678/s1](https://www.mdpi.com/article/10.3390/ijms26104678/s1)). References [73-84] are cited in the supplementary materials.  
[PERSON] performed the computation, interpreted the results, wrote the manuscript, and performed the submission. [PERSON] performed statistical analyses, participated in interpreting results, and prepared the heatmap figures. [PERSON], [PERSON] and [PERSON] performed physiological analysis. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] developed the theoretical background of the manuscript. [PERSON] conceived the idea, supervised the overall work, and wrote the manuscript. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data supporting the findings of this study are available within the article and Supplementary Material. The evaluated Bioprojects can be reached using the given accession number in Supplementary Table S2.  
[PERSON] and [PERSON] are grateful to CNPq and FUNCAP for the post-doctoral fellowship. [PERSON] is thankful to CNPq for the researcher fellowship (CNPq grant 313899/2021-5) and to FUNCAP and CAPES for continuous scientific support.  
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.