Improved Shoot Regeneration, Salinity Tolerance and Reduced Fungal Susceptibility in Transgenic Tobacco Constitutively Expressing PR-10a Gene.

Parinita Agarwal,Prashant More,Pradeep K Agarwal,Mitali Dabi,Kalyanashis Jana,Khantika Patel

doi:10.3389/fpls.2016.00217

Abstract

Plants in ecosystems are simultaneously exposed to abiotic and biotic stresses, which restrict plant growth and development. The complex responses to these stresses are largely regulated by plant hormones, which in turn, orchestrate the different biochemical and molecular pathways to maneuver stress tolerance. The PR-10 protein family is reported to be involved in defense regulation, stress response and plant growth and development. The JcPR-10a overexpression resulted in increased number of shoot buds in tobacco (Nicotiana tabacum), which could be due to high cytokinin to auxin ratio in the transgenics. The docking analysis shows the binding of three BAP molecules at the active sites of JcPR-10a protein. JcPR-10a transgenics showed enhanced salt tolerance, as was evident by increased germination rate, shoot and root length, relative water content, proline, soluble sugar and amino acid content under salinity. Interestingly, the transgenics also showed enhanced endogenous cytokinin level as compared to WT, which, further increased with salinity. Exposure of gradual salinity resulted in increased stomatal conductance, water use efficiency, photosynthesis rate and reduced transpiration rate. Furthermore, the transgenics also showed enhanced resistance against Macrophomina fungus. Thus, JcPR-10a might be working in co-ordination with cytokinin signaling in mitigating the stress induced damage by regulating different stress signaling pathways, leading to enhanced stress tolerance.

Highlights

Plants being sessile are strongly affected by climatic changes, pathogenic attack and these stresses represent a primary cause of crop-loss worldwide
In our earlier work (Agarwal et al, 2013), we reported the cloning of an important JcPR-10a gene from Jatropha curcas, an important biofuel crop grown in the wastelands of India
T0 Transgenic Lines The leaf explants transformed with JcPR-10a gene showed higher number (36) of shoot buds on regeneration medium as compared to VA (18) after 30 days of culture (Figures 1A,B)

Summary

Introduction

Plants being sessile are strongly affected by climatic changes, pathogenic attack and these stresses represent a primary cause of crop-loss worldwide These factors cause metabolic toxicity, membrane disorganization, closure of stomata, decreased photosynthetic activity, generation of reactive oxygen species (ROS) and altered nutrient acquisition (Hasegawa et al, 2000). Pathogenesis related-10 proteins are small proteins with cytosolic localization, conserved three dimensional structures, single intron and in some plant families the position is conserved at 62 amino acid (Hoffmann-Sommergruber et al, 1997). These proteins have a broad spectrum of roles in plants response to abiotic, biotic factors and toward growth and development. The RNase activity, ligand binding activity, posttranslational modification (phosphorylation) and phytohormone signaling provide some information into the mechanism of the regulation of PR-10 proteins, the presence of isoforms makes it difficult to decipher its exact mode of function

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Discussion

Conclusion