Decreased Expression of a Phosphoribosylanthranilate Transferase-Encoding Gene, OsPAT1, Causes Lesion Mimics in Rice

Area of Science:

• Plant molecular biology
• Plant genetics
• Biochemistry

Background:

• Lesion mimic mutants (LMMs) are crucial for studying plant defense and cell death mechanisms.
• The link between LMM phenotypes and primary nutrient biosynthesis is not well understood.
• Investigating novel LMMs can uncover new insights into plant stress responses.

Purpose of the Study:

• To characterize a novel rice LMM, designated lmm9, and identify the underlying genetic cause.
• To elucidate the role of the OsPAT1 gene in lesion mimic formation and plant defense.
• To explore the connection between OsPAT1 function, tryptophan biosynthesis, and plant cell death.

Main Methods:

• Map-based cloning and whole-genome sequencing to identify the causal mutation in lmm9.
• Genetic complementation and RNA interference (RNAi) assays to validate gene function.
• Yeast complementation assay and subcellular localization studies to analyze OsPAT1 variants.
• Transcriptional analysis of tryptophan biosynthesis pathway genes.

Main Results:

• A novel rice LMM (lmm9) was identified, exhibiting necrotic lesions, reduced agronomic traits, and increased mortality.
• The causal mutation was identified as a promoter insertion in OsPAT1, leading to its downregulation.
• Downregulation of OsPAT1 induced lesion mimic formation and was associated with upregulated tryptophan biosynthesis genes and increased tryptophan levels.

Conclusions:

• OsPAT1 plays a critical role in regulating plant defense and cell death in rice.
• Disruption of tryptophan biosynthesis is linked to the lesion mimic phenotype.
• This study enhances the understanding of metabolic homeostasis in plant stress responses and cell death regulation.