Date of Award

9-1-2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Agricultural and Environmental Sciences

First Advisor

Suping Zhou

Abstract

Transcription factor (TF) families played essential roles in plant responses to abiotic stress, contributing significantly to stress tolerance and adaptation. The basic helix-loop-helix (bHLH) TF family included 161 members in tomato (Solanum lycopersicum). Previous proteomic analysis identified TF bHLH148 (Solyc01g058670) as being upregulated under aluminum (Al) stress, suggesting a potential role in Al tolerance. To investigate this, CRISPR-Cas9 was used to generate SlbHLH148 knockout mutants in the ‘Black Vernissage’ tomato cultivar. Two homozygous T2 lines, Slbhlh148-1 and Slbhlh148-2, were confirmed to contain frameshift mutations that resulted in truncated proteins lacking the bHLH_AtIBH1_like domain, as shown by protein modeling. Phenotypic evaluation under Al stress revealed that the mutant lines were more sensitive to Al, as demonstrated by impaired morphological, physiological, and cellular traits. This suggested that SlbHLH148 played a positive role in Al tolerance and plant growth. Transcriptomic analysis provided insights into the molecular mechanisms by which SlbHLH148 contributed to Al stress adaptation. Disruption of SlbHLH148 also led to unstable seed germination under stress conditions, highlighting its role in early development. Additionally, significant changes in the concentrations of essential nutrients (Cu, K, Ca, Mg, Sr, and Mn) were observed, suggesting that bHLH148 was involved in nutrient homeostasis. Increased aluminum accumulation in the root tips of mutant lines pointed to impaired extracellular detoxification mechanisms. Overall, the SlbHLH148 mutation resulted in reduced biomass accumulation and diminished stress tolerance, indicating that bHLH148 was crucial for maintaining growth and adaptation under aluminum stress in tomato.

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