Wheat remembers the cold: Molecular changes prepare plants for the next chill

A cold spell may pass quickly, but wheat can carry its effects long after temperatures return to normal. Like many plants, wheat can be “primed” by mild stress and respond more effectively to next stresses. This phenomenon, known as stress memory, may help plants cope with varied environmental challenges. Against this backdrop, an important research question arises: how to memorize or maintain the memory of an earlier cold exposure after the cold itself disappears?

A new study published in The Crop Journal suggests that part of the answer lies in what happens between the two cold events. Researchers from Nanjing Agricultural University found that wheat continues to reorganize its physiology and gene regulation after an initial cold exposure, even after temperatures return to normal.

The researchers first exposed wheat seedlings to a non-lethal cold, then allowed the plants to fully recover, before challenging them again with an even stronger chill. “The exposed plants were much more tolerant to the next chilling, as exemplified by better photosystem II performance, less hydrogen peroxide accumulation, and retaining higher levels of key antioxidants,” shares co-corresponding author Xiao Wang.

Notably, some of these differences persisted after the first cold treatment had ended. “Recovery is therefore not a passive return to normal, but a key window in which wheat reorganizes its stress response while retaining a memory of earlier cold exposure,” says Wang.

Molecular data revealed that this memory was not simply the result of stress-response genes remaining switched on. Instead, many genes responded with a delay. Genes involved in jasmonic acid biosynthesis, heat-shock responses, protein folding, and other protective processes were only weakly activated immediately after the initial cold treatment but became much more active after the plants had returned to normal temperatures.

“This pattern suggests that the first cold exposure initiates a distinct post-stress regulatory program rather than merely prolonging the original stress response,” adds Wang. “These delayed responses were accompanied by lasting changes in histone modifications.”

In particular, selected stress-responsive genes gained H3K4me3, a mark generally associated with active transcription, or lost H3K27me3, which is commonly linked to repression. In several cases, these changes appeared before strong differences in gene expression became evident. “These suggest that the first cold exposure leaves molecular “bookmarks” at selected genes, helping preserve information from the earlier stress without keeping the plant continuously on high alert,” Wang explains.

The photosynthetic machinery revealed a second, more unexpected feature of this memory. Cold can damage photosystem components, forcing plants to replace damaged proteins and activate repair-related processes. “If previous cold exposure simply strengthened this repair system, primed plants might be expected to mount a stronger repair response when chilling returned,” Wang says.

Instead, the researchers observed the opposite: during subsequent chilling, plants without prior exposure strongly activated many genes associated with photosystem components and chloroplast protein synthesis, whereas primed plants showed a weaker induction of many of these genes even though their photosystem II remained in better condition.

“Primed plants did not repair more; they appeared to need less repair,” says Prof. Dong Jiang, co-corresponding author of the study. “Cold memory seems to protect the photosystem before extensive repairs.”

These findings point to enhanced photosystem tolerance, rather than intensive repair capacity alone, as an important feature of cold memory. “If the photosynthetic machinery suffers less damage, the plant may simply have less need to activate a large repair-and-replacement response,” adds Jiang.

Notably, signs of this altered behavior appeared before the second cold event: many photosystem-related genes had already acquired different histone-modification states while their transcript levels were still largely unchanged. In other words, molecular preparation for the next cold event had begun before the next cold arrived.

Together, the results place the post-stress phase at the center of a broader model of cold memory. The researchers proposed that further work will be needed to determine how chloroplast-derived signals interact with chromatin-regulating mechanisms in the nucleus.

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Author contact:

Dong Jiang (jiangd@njau.edu.cn) & Xiao Wang (xiaowang@njau.edu.cn)

About Professor Dong Jiang

Prof. Dong Jiang's research focuses on wheat yield and quality improvement, crop stress resilience, high-yield cultivation, and high-throughput crop phenotyping technologies. He serves as Director and Scientist of the Cultivation and Soil Fertility Division of China’s National Wheat-Industry Technology System. He has published more than 210 SCI-indexed papers, holds over 100 authorized patents, and has been recognized as an Elsevier Highly Cited Chinese Researcher for several consecutive years. He also holds leadership and advisory roles in national crop science and smart agriculture organizations.

About Professor Xiao Wang

Prof. Xiao Wang's research focuses on crop ecophysiology and stress resilience under climate change, particularly crop stress memory, priming-induced tolerance, and high-throughput crop micro-phenotyping. She is a key scientist in China's National Wheat-Industry Technology System and has published more than 80 SCI-indexed papers, authored four monographs, and holds more than 15 authorized national patents. She also contributes to international academic publishing and national agricultural disaster prevention and mitigation.

The publisher KeAi was established by Elsevier and China Science Publishing & Media Ltd to unfold quality research globally. In 2013, our focus shifted to open access publishing. We now proudly publish more than 300 world-class, open access, English language journals, spanning all scientific disciplines. Many of these are titles we publish in partnership with prestigious societies and academic institutions, such as the National Natural Science Foundation of China (NSFC).