Light and temperature effects on miR156 transgenic switchgrass flowering: A simulated latitudinal study

Area of Science:

• Plant Biotechnology
• Bioenergy Crops
• Molecular Genetics

Background:

• Controlling flowering in perennial grasses like switchgrass (Panicum virgatum L.) is crucial for optimizing lignocellulosic biomass production for bioenergy.
• Transgenic approaches, such as overexpressing the rice microRNA 156 (miR156) gene, show potential for delayed flowering, increased biomass, and altered cell wall traits in switchgrass.
• Reduced gene flow is a regulatory consideration for commercializing transgenic feedstocks, making delayed flowering a desirable trait for bioconfinement.

Purpose of the Study:

• To assess the impact of simulated latitudinal conditions on flowering and biomass production in transgenic switchgrass lines overexpressing miR156.
• To evaluate the potential of these transgenic lines for biomass production and breeding in different climatic zones, from tropical to cool-temperate.

Main Methods:

• Controlled growth chamber experiments simulating latitudinal gradients (tropical, subtropical, cool-temperate) using varying temperature and day length regimes.
• Assessment of flowering and reproduction in transgenic switchgrass lines (T-14, T-35, T-27, T-37) with different levels of miR156 overexpression.
• Measurement of plant biomass in transgenic lines under simulated tropical, subtropical, and cool-temperate conditions.

Main Results:

• Lower simulated latitudes (warmer temperatures, shorter days) promoted flowering in most miR156-overexpressing switchgrass lines, with tropical conditions rescuing flowering in all but line T-27.
• Lines T-35 and T-37 exhibited increased biomass under tropical conditions, while line T-14 showed more flowering in cool-temperate conditions.
• Biomass production varied by line and condition; T-14 and T-35 showed reduced biomass compared to controls in cool-temperate simulations.

Conclusions:

• Switchgrass engineered for miR156 overexpression can modulate flowering and biomass, with environmental conditions significantly influencing these traits.
• Tropical environments may be suitable for breeding miR156-overexpressing switchgrass lines, potentially enhancing bioconfinement and biomass yields.
• The findings support the use of miR156-engineered switchgrass for breeding programs aimed at improving biofuel feedstock characteristics.