Autophagic pathway contributes to low-nitrogen tolerance by optimizing nitrogen uptake and utilization in tomato

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Autophagy is essential for cellular recycling in eukaryotes.
• In plants, autophagy aids nutrient remobilization during starvation.
• The specific role of autophagy in nitrogen uptake and utilization was previously unknown.

Purpose of the Study:

• To investigate the role of the ATG6-dependent autophagic pathway in nitrogen (N) utilization in tomato plants under low-nitrogen (LN) conditions.
• To elucidate how autophagy influences N uptake, assimilation, and plant growth under LN stress.

Main Methods:

• Comparative analysis of wild-type (WT) tomato, autophagy-disrupted mutants (atg6), and ATG6-overexpressing lines under LN conditions.
• Assessment of biomass production, N accumulation, N transporter gene expression, and photosynthetic parameters.
• Enzyme activity assays for nitrate reductase and nitrite reductase.
• Grafting experiments to assess systemic regulation.

Main Results:

• ATG6-dependent autophagy regulates N utilization in tomato under LN stress.
• Autophagy-disrupted mutants showed reduced biomass and N content, while ATG6 overexpression enhanced these traits.
• ATG6-dependent autophagy positively impacts N transporter gene expression, N assimilation, carbon fixation, and photosynthetic efficiency.
• Grafting experiments indicated a non-cell-autonomous role for ATG6 in regulating N uptake and utilization.

Conclusions:

• ATG6-dependent autophagy is a key regulator of nitrogen uptake, utilization, and carbon assimilation in tomato plants under low-nitrogen conditions.
• Autophagy influences nutrient recycling, remobilization, and overall plant productivity in response to nitrogen deficiency.
• The findings highlight ATG6-dependent autophagy as a potential target for improving crop resilience to nitrogen-limiting environments.