RESEARCH-PGR: Cycling to low-temperature tolerance

Unseasonal cold spells annually cause significant losses in crops, impacting global food security and constraining growing ranges. This project focuses on understanding how sorghum, a low-input crop highly tolerant to drought and heat, can be made more resilient to low temperatures. Drawing inspiration from the natural circadian clock of plants and its connections to cold tolerance genes, daily fluctuations in transcripts, lipids, and metabolites crucial for low temperature tolerance are explored in Panicoid grasses, the plant family to which sorghum and maize belong.

Improving sorghum's low temperature tolerance could enhance agricultural sustainability in the U.S. Great Plains, mitigating the impact of unseasonal cold spells on crop yields. Additionally, current efforts to enhance low-temperature tolerance in crops comes at a cost to their overall health.

This project challenges traditional approaches to measuring and engineering low temperature tolerance in crops, by exploring the daily rhythms of plant responses to temperature changes. It has the potential to reshape how cold tolerance is understood and engineered in multiple crops. To raise public awareness of plant behaviors that change with daily rhythms, an interactive exhibit showcasing plant diurnal behaviors and their connection to low temperature tolerance will be created in collaboration with the Nebraska State Museum.

This exhibit, reaching Nebraskan rural schools through a traveling display, aims to inform and engage the public in the importance of these scientific discoveries for agriculture and food security.

The long-term goal of this project is to identify methods to mitigate fitness costs associated with increasing cold tolerance of sorghum through rhythmic regulation. To achieve this, a comparative analysis is conducted between sorghum and close genetic relative foxtail millet, which exhibits greater cold tolerance. The primary hypotheses driving the research are twofold: 1) The identification of key rhythmic transcripts and metabolites essential for cold tolerance in Panicoid grasses remains incomplete, and 2) The fitness cost associated with cold tolerance mechanisms can be counteracted through rhythmic expression.

These hypotheses are supported by preliminary data and tested through two objectives. First, identify novel transcripts and lipid and soluble metabolites critical to cold tolerance by their rhythmic response to cold. Building upon strong rhythmicity observed in transcript and lipid abundances in Panicoid grasses during preliminary investigations, this objective uses a combination of multiple omics and rhythmicity analyses to reveal previously unrecognized metabolic and transcriptional modules influencing low-temperature tolerance.

Identified module regulators will be expressed and tested for low-temperature tolerance in Arabidopsis as a proof of concept. Second, determine the extent of clock control of low temperature tolerance and identify promoter tools. Clock function is disrupted genetically in sorghum and by continuous light exposure in foxtail millet to assess their impact on low-temperature tolerance.

Potentially rhythmic promoters from the cold-tolerant foxtail millet will also be tested in the susceptible sorghum species to establish tools for tolerance engineering.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.