Date of Defense
27-5-2025 2:00 PM
Location
E1-1027
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Cellular and Molecular Biology
College
College of Science
Department
Biology
First Advisor
Prof. Khaled Amiri
Keywords
Salt Overly Sensitive (SOS) Signaling pathway, SOS1, SOS2, SOS3, Salt Stress, Avicennia marina, Arabidopsis thlaiana, Tomato.
Abstract
Abiotic stress is a major challenge for agricultural productivity. Salinity stress is a vital environmental constraint that significantly limits plant growth and reduce crop yield worldwide. Halophytes, such as Avicennia marina, offer unique opportunities to dissect adaptive mechanisms underlying salt tolerance. This study focuses on the structural and functional characterization of the Salt Overly Sensitive (SOS) pathway genes (SOS1, SOS2, SOS3) from A. marina. Full-length cDNAs of AmSOS1, AmSOS2, and AmSOS3 were cloned and characterized. The sequecne analysis of these genes compared to the respective orthologs revealed high similarities and conservation of all important domains. For AmSOS1 and AmSOS3, one isoform was identified. However, for AmSOS2, two isoforms were identified , AmSOS2-A and AmSOS2-B. These two distinct isoforms were idintified to be a result of alternative splicing. Furthermore, Structural modeling of these proteins based on a close ortholog illustrated the folding of each protein and highlited the similarities/differences to previous orthologs. Functional analysis demonstrated that AmSOS1, AmSOS2, and AmSOS3 were able to complement the respective mutations in Arabidopsis thaliana, restoring normal salt tolerance. The splice variant, isoform AmSOS2-B showed the ability to activate the SOS pathway in the sos3-1 mutant background but not in sos2-1, indicating the partial independence and functional plasticity of this variant. Protein–protein interaction studies confirmed the physical association between both SOS2 isoforms and the C-terminal domain of AmSOS1. Moreover, overexpression of AmSOS1, AmSOS2, and AmSOS3 in wild-type A. thaliana conferred enhanced salt tolerance, accompanied by reduced oxidative damage and improved physiological responses. In addition, AmSOS1 enhanced salt stress tolerance in transgenic tomato plants, which had better growth and yield compared to non transgenic tomato. Collectively, These results confirm that the cloned A. marina SOS genes are functional orthologs. Their ability to enhance salt stress tolerance in Arabidopsis thaliana and tomato plants underscores their value for the development of salt-tolerant crop varieties.
STRUCTURAL AND FUNCTIONAL CHARACTERIZATION OF SOS PATHWAY GENES (SOS1, SOS2, SOS3) IN AVICENNIA MARINA: INSIGHTS INTO SALINITY STRESS TOLERANCE
E1-1027
Abiotic stress is a major challenge for agricultural productivity. Salinity stress is a vital environmental constraint that significantly limits plant growth and reduce crop yield worldwide. Halophytes, such as Avicennia marina, offer unique opportunities to dissect adaptive mechanisms underlying salt tolerance. This study focuses on the structural and functional characterization of the Salt Overly Sensitive (SOS) pathway genes (SOS1, SOS2, SOS3) from A. marina. Full-length cDNAs of AmSOS1, AmSOS2, and AmSOS3 were cloned and characterized. The sequecne analysis of these genes compared to the respective orthologs revealed high similarities and conservation of all important domains. For AmSOS1 and AmSOS3, one isoform was identified. However, for AmSOS2, two isoforms were identified , AmSOS2-A and AmSOS2-B. These two distinct isoforms were idintified to be a result of alternative splicing. Furthermore, Structural modeling of these proteins based on a close ortholog illustrated the folding of each protein and highlited the similarities/differences to previous orthologs. Functional analysis demonstrated that AmSOS1, AmSOS2, and AmSOS3 were able to complement the respective mutations in Arabidopsis thaliana, restoring normal salt tolerance. The splice variant, isoform AmSOS2-B showed the ability to activate the SOS pathway in the sos3-1 mutant background but not in sos2-1, indicating the partial independence and functional plasticity of this variant. Protein–protein interaction studies confirmed the physical association between both SOS2 isoforms and the C-terminal domain of AmSOS1. Moreover, overexpression of AmSOS1, AmSOS2, and AmSOS3 in wild-type A. thaliana conferred enhanced salt tolerance, accompanied by reduced oxidative damage and improved physiological responses. In addition, AmSOS1 enhanced salt stress tolerance in transgenic tomato plants, which had better growth and yield compared to non transgenic tomato. Collectively, These results confirm that the cloned A. marina SOS genes are functional orthologs. Their ability to enhance salt stress tolerance in Arabidopsis thaliana and tomato plants underscores their value for the development of salt-tolerant crop varieties.
