NAC-mediated membrane lipid remodeling negatively regulates fruit cold tolerance

Area of Science:

• Plant Biology
• Molecular Biology
• Biochemistry

Background:

• Low temperatures damage fruit cell membranes by altering phospholipid composition, leading to chilling injury.
• Phosphatidic acid, a key plant lipid second messenger, accumulates under stress, but its production pathway is unclear.
• Understanding cold tolerance mechanisms in fruits is crucial for preventing post-harvest losses.

Purpose of the Study:

• To investigate the role of NAC transcription factors in banana fruit cold tolerance.
• To elucidate the regulatory mechanisms of phosphatidic acid production during cold stress.
• To explore the interplay between ethylene and NACs in membrane lipid remodeling.

Main Methods:

• Identification and characterization of cold-responsive NAC transcription factors (MaNAC25, MaNAC28) in bananas.
• Analysis of gene expression related to phospholipid degradation and phosphatidic acid synthesis.
• Investigating the regulatory interactions between NACs, ethylene, and membrane lipid metabolism in banana and transgenic tomato fruits.

Main Results:

• MaNAC25 and MaNAC28 were identified as negative regulators of cold tolerance in banana fruits.
• These NACs upregulate phospholipid degradation genes, increasing phosphatidic acid levels via a positive feedback loop.
• Ethylene was found to directly inhibit phospholipid degradation and reduce NAC activity in both banana and tomato.

Conclusions:

• NAC transcription factors (MaNAC25, MaNAC28) negatively regulate cold tolerance in fruits through membrane lipid remodeling.
• A positive feedback loop involving NACs promotes phospholipid degradation and phosphatidic acid accumulation under cold stress.
• Ethylene acts as a protective agent by inhibiting this NAC-mediated degradation pathway, enhancing cold tolerance.