Jasmonate is a lipid-based plant hormone that acts as an internal messenger, coordinating a plant’s response to its surroundings and guiding its development. The hormone’s name is derived from the jasmine plant, where a volatile form called methyl jasmonate was first identified as a component of the flower’s signature aroma. This family of hormones is synthesized from fatty acids, specifically linolenic acid, through a series of steps that begin in the chloroplasts.
A Plant’s Defense System
Jasmonate functions as a primary alarm system when a plant faces an attack from a living organism, known as biotic stress. When an herbivore, such as a caterpillar, chews on a leaf, the physical damage triggers a rapid synthesis of jasmonate at the wound site. This surge of hormones initiates a cascade of defensive actions throughout the plant. The signaling pathway is complex, involving the degradation of repressor proteins called JAZ, which then allows defense-related genes to be activated.
Once activated, this internal signal travels through the plant’s tissues, preparing other areas for potential attack. A primary result is the production of compounds that make the plant less appealing or even toxic to the herbivore. For example, a tomato plant under attack will produce specific molecules that interfere with an insect’s ability to digest the leaf tissue.
The defense strategy extends beyond internal chemical changes. Jasmonate signaling can also prompt the plant to release specific volatile organic compounds (VOCs) into the air. These airborne chemicals act as a distress signal, attracting natural predators of the attacking insects. Furthermore, these VOCs can be detected by neighboring plants, which then ramp up their own defense systems in anticipation of a threat, a phenomenon that showcases a form of plant-to-plant communication.
Regulating Growth and Development
Beyond its role in defense, jasmonate is involved in regulating a plant’s life cycle. The hormone influences various developmental processes, from the formation of roots to the timing of reproduction and aging. In many cases, jasmonate’s effect on growth is inhibitory, a trade-off that allows the plant to redirect resources toward defense or survival when needed.
One clear example of its developmental function is in the formation of storage organs. High levels of jasmonate encourage the accumulation of storage proteins, which is why it is associated with the development of tubers in plants like potatoes. The hormone directly activates the genes responsible for producing these vegetative storage proteins.
Jasmonate also has a function in plant reproduction. It is involved in multiple aspects of flower development, including the maturation of pollen. Proper jasmonate signaling is necessary for producing viable pollen, so disruption in its biosynthesis can hinder successful reproduction. Later in the plant’s life, jasmonate contributes to senescence, the natural aging process that includes the yellowing and eventual dropping of leaves, by promoting the breakdown of photosynthetic machinery.
Responding to Environmental Stress
Plants also rely on jasmonate to navigate challenges posed by their non-living, or abiotic, environment. The hormone helps orchestrate physiological adjustments that enhance survival during periods of stress. These responses are distinct from the defense mechanisms triggered by herbivores or pathogens and are geared toward tolerating difficult environmental conditions.
During a drought, for instance, jasmonate signaling can help a plant conserve water. The hormone can influence the behavior of stomata, the small pores on a leaf’s surface that control gas exchange and water transpiration. By regulating stomatal closure, the plant can reduce water loss and better withstand dry conditions. This response is part of a larger, complex network where jasmonate interacts with other hormones to manage the plant’s internal water balance.
Exposure to high salinity in the soil or excessive ultraviolet (UV) radiation are other abiotic stressors where jasmonate plays a part. The hormone helps to mitigate the cellular damage these conditions can cause. The signaling pathways activated by jasmonate in these scenarios help the plant to fortify itself against the environmental pressures.
Applications in Agriculture and Industry
The scientific understanding of jasmonate has led to practical applications in agriculture. Synthetic versions of the hormone can be applied to crops to “prime” their defense systems, making them more resistant to subsequent pest infestations. When treated with jasmonates, the plant begins to produce defensive compounds and is ready to respond more quickly and robustly if an herbivore begins feeding. This pre-emptive activation can reduce the reliance on conventional chemical pesticides.
Beyond the fields, jasmonate has commercial value in the fragrance and cosmetics industries. The volatile form of the hormone, methyl jasmonate, is a prized ingredient in perfumes for its distinctive jasmine scent. Its discovery originated from the analysis of jasmine oil, and its chemical properties are now harnessed to create fragrances and other scented products.