A vegetative storage protein improves drought tolerance in maize

Area of Science:

• Plant Biology
• Crop Science
• Molecular Biology

Background:

• Vegetative storage proteins (VSPs) are vital nitrogen reserves in dicots but have not been identified in grasses, a major global crop group.
• Understanding nitrogen storage mechanisms in grasses like maize is crucial for improving crop resilience and yield.

Purpose of the Study:

• To identify and characterize a novel VSP in maize.
• To investigate the role of this VSP in nitrogen storage and drought tolerance.
• To assess the potential of VSP overexpression for enhancing maize crop performance.

Main Methods:

• Identification and characterization of a maize lipoxygenase (ZmLOX6) as a VSP.
• Ectopic expression of ZmLOX6 in maize using tissue-specific promoters, focusing on mesophyll cells.
• Field trials evaluating transgenic maize hybrids under managed drought stress.

Main Results:

• Overexpression of ZmLOX6 in maize mesophyll cells led to a fivefold increase in VSP accumulation.
• Transgenic maize hybrids overexpressing ZmLOX6 exhibited significantly improved grain yield under drought stress.
• The identified VSP was effectively remobilized from leaves during grain development, similar to other major proteins.

Conclusions:

• Maize possesses a functional VSP (ZmLOX6) that can be targeted to chloroplasts and accumulated in mesophyll cells.
• Overexpressing ZmLOX6 enhances maize drought tolerance and grain yield, offering a new strategy for crop improvement.
• This discovery opens avenues for engineering nitrogen storage in grasses to mitigate climate change impacts on agriculture.