Research

Decoding Stress-Induced Leaf Senescence in Tomato

Leaves are central to plant productivity, and understanding how they age is essential for improving crop performance. My research focuses on uncovering the molecular mechanisms that regulate leaf senescence, particularly under environmental stress conditions.

Leaf senescence is a highly regulated developmental process, often visible as the transition from green to yellow. While this process occurs naturally, environmental stresses such as salinity can accelerate senescence, leading to reduced plant productivity. Plant hormones, especially cytokinins, play a critical role in delaying this process and maintaining leaf function.

My doctoral research investigates how cytokinin signaling and transcriptional regulation interact to control stress-induced leaf senescence in tomato, with a particular focus on salt stress.

Research Focus
  • Molecular regulation of leaf senescence
  • Cytokinin-mediated stress responses
  • Gene expression dynamics under salt stress
  • Integration of transcriptomics and functional genomics
Research Projects

Project 1 (Completed)

Published: Thennakoon, M., Khanna, R.R., Singh, S. et al. cis-Zeatin is an Active Cytokinin that Mediates Gene Expression and Delays Leaf Senescence in Tomato Under Salt Stress. J Plant Growth Regul (2026). https://doi.org/10.1007/s00344-026-12102-5

cis-Zeatin is an Active Cytokinin that Mediates Gene Expression and Delays Leaf Senescence in Tomato Under Salt Stress

This project examined the effects of two cytokinin types; cis-Zeatin and trans-Zeatin in delaying leaf senescence in tomato plants exposed to salt stress.

Approach:
  • Senescence assays and phenotypic characterization
  • Salt stress treatments under controlled conditions
  • RNA-seq data generation and analysis
  • Differential gene expression analysis
  • Weighted Gene Co-expression Network Analysis (WGCNA)
  • Pathway enrichment analysis
  • Integration of hormone and stress-response datasets
Key Outcomes:
  • Insights into cytokinin biosynthesis and signaling pathways
  • Discovery of candidate genes linked to stress adaptation in organelle level that are significantly regulated by cis-Zeatin

Thennakoon et al., 2026


Intracellular cytokinin (CK) transcriptome effects of cis-Zeatin (cZ) and trans-Zeatin (tZ) (A) Gene Ontology (GO) term enrichment for organelle-specific genes, including nucleus, Endoplasmic Reticulum (ER), chloroplast, and plastids - Text color indicates GO terms shared between cZ and tZ (blue) or uniquely associated with tZ (brown) or cZ (purple) (B) Distribution of unique and shared differentially expressed genes (DEGs) regulated by cZ and tZ within each organelle - Upward triangles indicate upregulated genes, and downward triangles indicate downregulated genes. (C) Conceptual model of intracellular CK regulation - Solid arrows represent regulation supported by GO term enrichment in this study, whereas dashed arrows indicate potential regulatory interactions not directly identified from the current GO analysis.




Project 2 (Ongoing)


Role of Cytokinin Response factor 5 (SlCRF5) in Leaf Senescence

This project focuses on validating the functional role of selected candidate genes identified from transcriptomic analyses.



A) Cytokinin Two Component Signaling Pathway and the Cytokinin Response Factors Association B) Domains of Cytokinin Response factors C) Response of SlCRF5 in responding to salt stress










Approach:
  • Mutant characterization
  • Gene expression analysis (qPCR)
  • Plasmid construction and molecular cloning
Expected Outcomes:
  • Functional validation of regulatory genes
  • Improved understanding of cytokinin-mediated pathways
  • Identification of targets for enhancing stress tolerance and delaying senescence

Methods & Technical Expertise

Molecular Genetics & Functional Genomics
  • Gene cloning and plasmid construction
  • Mutant characterization
  • Gene overexpression systems
Transcriptomics & Data Analysis
  • RNA-seq pipeline analysis
  • Differential gene expression analysis
  • Network analysis (WGCNA)
  • Statistical analysis using R
  • Data visualization
Plant Stress Physiology
  • Salt stress assays
  • Hormone treatment experiments
  • Senescence phenotyping
  • Controlled environment growth experiments

Applied Impact

This research contributes to identifying molecular targets that can improve crop performance under salinity stress. By understanding how hormonal regulation controls senescence, this work supports the development of strategies for enhancing plant resilience and productivity, with potential applications in agricultural biotechnology.