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The ability of plants to protect themselves from stress-related damages is termed “adaptability” and the phenomenon of showing better performance in subsequent stress is termed “stress memory”. This phenomenon has been reported in various stresses such as drought, heat, salinity, cold, and heavy metal toxicity. Histone modification leading to chromatin remodeling and accumulation of phosphorylated RNA polymerase on the promoters of memory genes is a well-known mechanism of plant stress memory. Recent studies have revealed the role of non-coding RNAs (ncRNAs) and alternative splicing (AS) in memory-specific gene expression and transgenerational inheritance of stress memory. MicroRNAs (miRNAs) inhibit specific genes to enable plants to respond better in subsequent drought and heat stress, while long non-coding RNAs (lncRNAs) play roles in epigenetic regulation of memory gene expression in cold and salt stress. Small interfering RNAs (siRNAs) lead to DNA methylation during the memory response of biotic, salt, and heavy metal stress. Simultaneously, stress-responsive isoforms of tolerant genes are found to be expressed as a memory response in subsequent heat stress. This review highlights the stress-type-specific roles of ncRNAs and AS in establishing, maintaining, and transmitting stress memory, offering insights into their potential for improving crop resilience through genetic and epigenetic priming strategies.

In the natural environment, plants are often bombarded by a combination of abiotic (such as drought, salt, heat or cold) and biotic (necrotrophic and biotrophic pathogens) stresses simultaneously. It is critical to understand how the various response pathways to these stresses interact with one another within the plants, and where the points of crosstalk occur which switch the responses from one pathway to another. Calcium sensors are often regarded as the first line of response to external stimuli to trigger downstream signaling. Abscisic acid (ABA) is a major phytohormone regulating stress responses, and it interacts with the jasmonic acid (JA) and salicylic acid (SA) signaling pathways to channel resources into mitigating the effects of abiotic stresses versus defending against pathogens. The signal transduction in these pathways are often carried out via GTP-binding proteins (G-proteins) which comprise of a large group of proteins that are varied in structures and functions. Deciphering the combined actions of these different signaling pathways in plants would greatly enhance the ability of breeders to develop food crops that can thrive in deteriorating environmental conditions under climate change, and that can maintain or even increase crop yield.

The capability of a plant to protect itself from stress-related damages is termed “adaptability” and the phenomenon of showing better performance in subsequent stress is termed “stress memory”. While drought is one of the most serious disasters to result from climate change, the current understanding of drought stress priming in soybean is still inadequate for effective crop improvement. To fill this gap, in this study, the drought memory response was evaluated in cultivated soybean (Glycine max). To determine if a priming stress prior to a drought stress would be beneficial to the survival of soybean, plants were divided into three treatment groups: the unprimed group receiving one cycle of stress (1S), the primed group receiving two cycles of stress (2S), and the unstressed control group not subjected to any stress (US). When compared with the unprimed plants, priming led to a reduction of drought stress index (DSI) by 3, resulting in more than 14% increase in surviving leaves, more than 13% increase in leaf water content, slight increase in shoot water content and a slower rate of loss of water from the detached leaves. Primed plants had less than 60% the transpiration rate and stomatal conductance compared to the unprimed plants, accompanied by a slight drop in photosynthesis rate, and about a 30% increase in water usage efficiency (WUE). Priming also increased the root-to-shoot ratio, potentially improving water uptake. Selected genes encoding late embryogenesis abundant (LEA) proteins and MYB, NAC and PP2C domain-containing transcription factors were shown to be highly induced in primed plants compared to the unprimed group. In conclusion, priming significantly improved the drought stress response in soybean during recurrent drought, partially through the maintenance of water status and stronger expression of stress related genes. In sum, we have identified key physiological parameters for soybean which may be used as indicators for future genetic study to identify the genetic element controlling the drought stress priming.