Hello crops. Stress and potential damage are on the way. We have some extreme heat conditions headed our way. We know what is going to happen. Our reactive oxygen species (ROS) will react and develop an imbalance. What we can expect from this abiotic stress can influence our production. If severe enough and left unchecked, we could even see death of the plant. Hopefully our crop advisors and managers recognize the potential problem and communicate with us.
First, they need to understand ROS and the negative impact it can have on the crop. This includes cellular damage at varying levels, some as severe as plant death and some as mild as damage that might allow the plant to survive but can cause poor-quality fruit, nuts or vegetables to develop. High ROS levels can damage cell membranes (lipid peroxidation), nucleic acids (DNA) and proteins, leading to cell dysfunction and potential death.
Oxidative stress can be caused by the imbalance of ROS production. This can negatively impact plant growth, development and survival. Damage this year from the heat could seriously reduce flowering and crop set in the next season. ROS target DNA, RNA, proteins and lipids, disrupting their functions and causing cellular damage. It might be so mild that we think we are having a good crop year. The fact is, even a slight impact can reduce yield and quality so our full potential cannot be achieved.
ROS act as signaling molecules. These signals trigger transduction pathways so we can respond appropriately to abiotic and biotic stresses. ROS also become involved in regulating plant development, cell division, differentiation and elongation. Cell division directly affects fruit and nut size, leaf size and even bud size. The process of cell differentiation has many key roles in our plant development. Meristematic cells at the tips of roots and shoots can reduce elongation so branches can be short or not grow. Interference in root hair tips can reduce our ability to take up adequate nutrients.
Imbalance can prevent structural change in our cells so we cannot produce stronger cell walls for tree limbs to support our crop load or perhaps reduce a wheat crop stem’s ability to withstand wind or water weight, so we lose production through lodging. Some altered and prevented cell differentiation might reduce water transportation, nutrient storage and our defense.

The Role of ROS in Photosynthesis, Gene Expression and Plant Defense
ROS can have both positive and negative impacts on photosynthesis. While excess ROS can damage photosynthetic components, they also play a role in signaling pathways that allow plants to acclimate to environmental changes and even serve as a form of protection against excess light. An excess of ROS could result in damage to the photosynthetic machinery. Damage to proteins, amino acid residues, lipid peroxidation and DNA could impair our efficiency, capture and electron transport.
ROS have positive roles such as chloroplast-nucleus signaling pathways. These pathways communicate changes in environmental conditions such as the high heat coming our way. They can signal high light stress and initiate our internal responses to protect ourselves. They are the trigger that signals pathways to allow us to acclimate to environmental stress like high light and drought. ROS communicate to us by modulating gene expression. We have defense mechanisms against biotic and abiotic stressors, including infections and pathogens.
Again, when this ROS balance is off it can seriously damage us. So how can our crop consultants help us? It is called communication. This communication can be achieved by a process called gene upregulation. In gene regulation, upregulation refers to an increase in the expression of a gene, leading to more protein production while downregulation refers to a decrease in gene expression, leading to less protein production. Essentially, upregulation “turns on” a gene while downregulation “turns off” a gene.
To explain, we have these examples: Increased expression is a higher level of transcription (RNA production) or translation (protein production) of a gene. More proteins are encoded by that gene. An upregulation can occur when a cell needs to produce more receptors to become more sensitive to a hormone. This can be triggered by signals within the cell itself or other cells as well as by environmental clues.
Downregulation involves lower levels of transcription or translation, which is the reverse of upregulation. Fewer proteins are therefore encoded. Now signals change so a decrease in production of receptors makes a cell less sensitive to that same hormone. Since the downregulation can be triggered by the same factors and the signals come from the same sources, upregulation and downregulation are two sides of the same coin.

Upregulation
• Purpose: Increases the production of specific proteins often in response to stress or specific signals to promote adaptation and survival.
• Examples: Plants may upregulate genes involved in defense against pathogens (like R-genes in tomato and potato) or stress tolerance (like those involved in cold or heat stress).
• Mechanism: Can involve increased transcription (the process of creating mRNA from DNA) or increased translation (the process of creating protein from mRNA) or both.
Downregulation
• Purpose: Decreases the production of specific proteins, often to reduce the intensity of a particular process or to conserve resources.
• Examples: Plants may downregulate genes related to growth or development when facing stress, such as drought or nutrient deficiency.
• Mechanism: Can involve decreased transcription or translation or both, or by affecting the stability of the mRNA or the produced protein.
Regulation and Examples
• Regulatory genes: Many genes are involved in regulating the expression of other genes. These regulatory genes encode transcription factors that can bind to DNA and either activate or repress other genes influencing their expression levels.
• Stress response: Plants respond to environmental stresses like drought, nutrient deficiency or pathogen attack by upregulating defense genes and downregulating genes related to normal growth and development.
• Example of specific gene expression changes (pathogen response): Studies on tomato and potato R-genes have shown that a large portion of R-genes are upregulated in response to pathogens, indicating a defense response.

A consultant could recommend a biostimulant to aid in gene upregulation. Biostimulants can upregulate specific genes in plants, influencing various biological processes. For instance, they can increase the expression of genes related to photosynthesis, nutrient uptake, stress response and growth-promoting factors. Some of the ways biostimulants work are:
• Hormone-mimicking actions: Some biostimulants mimic plant hormones triggering the upregulation of specific genes involved in growth and development.
• Enzyme/protein function regulation: Biostimulants can influence the expression of genes coding for enzymes and proteins involved in various metabolic pathways leading to increased activity of these molecules.
• Transcriptional regulatory pathways: Biostimulants can interact with transcriptional regulatory networks influencing the binding of transcription factors to DNA and activating the expression of specific genes. Biostimulants can upregulate genes involved in photosynthetic processes leading to increased chlorophyll content and photosynthetic efficiency. Alfalfa-based protein hydrolysates have been shown to upregulate genes involved in nutrient uptake, such as phosphate and nitrogen transporters. Biostimulants can upregulate genes involved in stress tolerance like those involved in antioxidant defense and osmoprotection, helping plants cope with adverse environmental conditions like drought or salinity. Biostimulants can increase the expression of growth-promoting genes, leading to enhanced plant growth and development.
Overall, biostimulants act as signaling molecules that modulate gene expression in plants leading to improved growth, stress tolerance and quality traits. They come in many different forms: acids, microbials, extracts and others. The message I am sending with this letter to crops is that there is help. Through communication within the plant aided by the outside influence of biostimulants, we can protect ourselves against abiotic stressors as well as biotic stressors.