Clesivan Pereira dos Santos

Ascorbic acid (AsA) is an essential plant metabolite that acts primarily as an antioxidant, regulates cell division and elongation, and enhances stress tolerance. Despite its crucial physiological role, the biosynthesis of AsA in G. max, a major crop of significant commercial importance, remains largely unexplored. This gap highlights the need for a thorough investigation of AsA biosynthesis pathways and their role in optimizing the nutritional value and stress tolerance of soybeans. This study identified 41 key genes linked to four AsA biosynthesis pathways in G. max, highlighting specific gene duplications compared to Arabidopsis. Their expression levels were assessed by analyzing a diverse set of RNA-Seq data from the NCBI database. Additionally, to cross-validate the expression levels of genes and the accumulation levels of AsA in the principal tissues, G. max plants were grown under controlled conditions following the protocols from selected RNA-seq experiments. Genes associated with the D-mannose/L-galactose pathway exhibited ubiquitous expression, and the expression patterns of genes from alternative pathways reflected their responsiveness to specific tissues or environmental conditions. Germination and leaf development were accompanied by strong expression of gene members from all pathways, whereas leaf aging was characterized by downregulation. Specific gene members, such as GMP_2a (D-mannose/L-galactose pathway), GulLO_1f (L-gulose pathway), and MIOX_3a (Myo-inositol pathway) were highly stress-responsive and linked to stress-resistant genotypes and cultivars. Consistent with gene expression analyses, the quantification of AsA revealed the highest mass fractions in young leaves and germinating seeds. However, AsA mass fractions were significantly reduced or unchanged under stress conditions, depending on the type of stress and the duration of exposure. Overall, this study validated the relevance of AsA biosynthesis pathways in soybeans, highlighting key genes that could be targeted to enhance stress tolerance and improve ascorbate production, thereby boosting the nutritional value of soybeans.

Pepper (Capsicum annuum L.) is a vegetable consumed worldwide, primarily used for vitamin C uptake and condiment purposes. Ascorbate (Asc) is a multifunctional metabolite, acting as an antioxidant and enzymatic cofactor involved in multiple cellular processes. Nevertheless, there is no evidence about the contribution of biosynthesis pathways and regulatory mechanisms responsible for Asc reserves in pepper plants. Here, we present a genome- and transcriptome-wide investigation of genes responsible for Asc biosynthesis in pepper during fruit development, stresses, and phytohormone exposures. A total of 21 genes, scattered in ten of twelve pepper chromosomes were annotated. Gene expression analyses of nine transcriptomic experiments supported the primary role of the L-galactose pathway in the Asc-biosynthesizing process, given its constitutive, ubiquitous, and high expression profile observed in all studied conditions. However, genes from alternative pathways generally exhibited low expression or were unexpressed and appeared to play some secondary role under specific stress conditions and phytohormone treatments. Taken together, our findings provide a deeper spatio-temporal understanding of expression levels of genes involved in Asc biosynthesis, and they highlight GGP2, GME1 and 2, and GalLDH members from L-galactose pathway as promising candidates for future wet experimentation, addressing the attainment of increase in ascorbate content of peppers and other crops.

Identifying cultivars of leguminous crops exhibiting drought resistance has become crucial in addressing water scarcity issues. This investigative study aimed to select soybean and cowpea cultivars with enhanced potential to grow under water restriction during the vegetative stage. Two parallel trials were conducted using seven soybean (AS3810IPRO, M8644IPRO, TMG1180RR, NS 8338IPRO, BMX81I81IPRO, M8808IPRO, and BÔNUS8579IPRO) and cowpea cultivars (Aracê, Novaera, Pajeú, Pitiúba, Tumucumaque, TVU, and Xique-xique) under four water levels (75, 60, 45, and 30% field capacity—FC) over 21 days. Growth, water content, membrane damage, photosynthetic pigments, organic compounds, and proline levels were analyzed. Drought stress significantly impacted the growth of both crops, particularly at 45 and 30% FC for soybean and 60 and 45% FC for cowpea plants. The BÔNUS8579IPRO and TMG1180RR soybean cultivars demonstrated the highest performance under drought, a response attributed to increased amino acids and proline contents, which likely help to mitigate membrane damage. For cowpea, the superior performance of the drought-stressed Xique-xique cultivar was associated with the maintenance of water content and elevated photosynthetic pigments, which contributed to the preservation of the photosynthetic efficiency and carbohydrate levels. Our findings clearly indicate promising leguminous cultivars that grow under water restriction, serving as viable alternatives for cultivating in water-limited environments.