Engineering 6-phosphogluconate dehydrogenase improves grain yield in heat-stressed maize

Area of Science:

• Plant Biology
• Biochemistry
• Genetics

Background:

• Endosperm starch synthesis is crucial for maize grain yield.
• High-temperature stress negatively impacts starch accumulation.
• The enzyme 6-phosphogluconate dehydrogenase (6PGDH) plays a key role in this process.

Purpose of the Study:

• To investigate the heat sensitivity of different 6PGDH isozymes in maize.
• To engineer heat-stable 6PGDH for enhanced function in the endosperm.
• To assess the impact of this engineering on maize grain yield under heat stress.

Main Methods:

• Identified heat-stable cytosolic 6PGDH isozymes (PGD1, PGD2) and heat-labile amyloplast-localized PGD3.
• Created fusion proteins (WPGD1, WPGD2) by targeting heat-stable isozymes to amyloplasts using the Waxy1 targeting sequence.
• Generated transgenic maize expressing WPGD1 and WPGD2 under an endosperm-specific promoter.

Main Results:

• Fusion proteins were successfully targeted to amyloplasts and showed enhanced heat stability.
• Transgenic plants exhibited increased 6PGDH activity in kernels.
• WPGD1 and WPGD2 expression mitigated yield loss under high-nighttime-temperature conditions by increasing kernel number.

Conclusions:

• The amyloplast pentose phosphate pathway is a heat-sensitive metabolic step in maize kernel development.
• Engineering heat-stable 6PGDH in amyloplasts can improve maize resilience to heat stress and maintain grain yield.
• This study offers insights into metabolic engineering for crop improvement.