This research aims to unravel the regulatory networks and adaptive molecular mechanisms that drive salinity resilience in mango cultivars with varying salt stress responses. The study examined the molecular characteristics of three key proline metabolism genes: pyrroline carboxylate synthetase (P5CS), pyrroline carboxylate reductase (P5CR), and pyrroline carboxylate dehydrogenase (P5CDH) in mango under salinity stress conditions. The homology search of assembled transcripts revealed orthologs within the Malvids clade, which includes the order Sapindales and the Anacardiaceae family. A total of 19 unigenes associated with glutamate-mediated proline biosynthesis were identified, comprising seven P5CS (three isoforms), ten P5CR, and two P5CDH coding sequences. Phylogenetic analysis demonstrated strong homology with Anacardiaceae mRNA, whereas genes from other plant families formed distinct clades. Notably, P5CDH displayed unique phylogenetic relationships within Anacardiaceae, with Mangifera indica and Pistacia vera clustering closely together. In contrast, P5CR sequences exhibited the highest variability and segregated into separate clusters from orthologs of other families and orders. P5CS was identified as a key regulator of proline biosynthesis, featuring conserved amino acid kinase (AAK) and aldehyde dehydrogenase (ADH) domains essential for osmotic adjustment. The predicted cytoplasmic localization of P5CS and P5CR proteins could be a valid explanation for proline accumulation under stress, while mitochondrial localization predicted for pyrroline carboxylate dehydrogenase (P5CDH) protein is likely to regulate proline turnover. When exposed to salt stress, all mango varieties studied significantly increased their pyrroline carboxylate synthetase (P5CS) and pyrroline carboxylate reductase (P5CR) gene activity to produce more proline, likely helping plants mitigate stress. The variety ‘Kurukkan’ showed the highest increase in both genes, suggesting its strong salt resilience associated to its high proline production. In contrast, ‘Amrapali’ increased its P5CDH gene activity, which breaks down proline, which may account for its decreased salt tolerance. The presence of multiple isoforms and lineage-specific divergence in proline biosynthesis genes underscores the importance of this pathway in stress adaptation. Proline pathway genes that are functionally validated through heterologous expression in model organisms could serve as valuable targets for genome editing aimed at developing rootstocks that tolerate salinity or could be utilized as potential genetic resources for breeding resistant varieties.

Evolutionary and Structural Insights into Proline Metabolism Genes Associated with Salt Resilience in Mango

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发表日期：

2026年4月30日

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Laxmi Rastogi,
Anju Bajpai,
Sumit K. Soni,
M. Muthukumar

摘要

This research aims to unravel the regulatory networks and adaptive molecular mechanisms that drive salinity resilience in mango cultivars with varying salt stress responses. The study examined the molecular characteristics of three key proline metabolism genes: pyrroline carboxylate synthetase (P5CS), pyrroline carboxylate reductase (P5CR), and pyrroline carboxylate dehydrogenase (P5CDH) in mango under salinity stress conditions. The homology search of assembled transcripts revealed orthologs within the Malvids clade, which includes the order Sapindales and the Anacardiaceae family. A total of 19 unigenes associated with glutamate-mediated proline biosynthesis were identified, comprising seven P5CS (three isoforms), ten P5CR, and two P5CDH coding sequences. Phylogenetic analysis demonstrated strong homology with Anacardiaceae mRNA, whereas genes from other plant families formed distinct clades. Notably, P5CDH displayed unique phylogenetic relationships within Anacardiaceae, with Mangifera indica and Pistacia vera clustering closely together. In contrast, P5CR sequences exhibited the highest variability and segregated into separate clusters from orthologs of other families and orders. P5CS was identified as a key regulator of proline biosynthesis, featuring conserved amino acid kinase (AAK) and aldehyde dehydrogenase (ADH) domains essential for osmotic adjustment. The predicted cytoplasmic localization of P5CS and P5CR proteins could be a valid explanation for proline accumulation under stress, while mitochondrial localization predicted for pyrroline carboxylate dehydrogenase (P5CDH) protein is likely to regulate proline turnover. When exposed to salt stress, all mango varieties studied significantly increased their pyrroline carboxylate synthetase (P5CS) and pyrroline carboxylate reductase (P5CR) gene activity to produce more proline, likely helping plants mitigate stress. The variety ‘Kurukkan’ showed the highest increase in both genes, suggesting its strong salt resilience associated to its high proline production. In contrast, ‘Amrapali’ increased its P5CDH gene activity, which breaks down proline, which may account for its decreased salt tolerance. The presence of multiple isoforms and lineage-specific divergence in proline biosynthesis genes underscores the importance of this pathway in stress adaptation. Proline pathway genes that are functionally validated through heterologous expression in model organisms could serve as valuable targets for genome editing aimed at developing rootstocks that tolerate salinity or could be utilized as potential genetic resources for breeding resistant varieties.