Jasmonate

The jasmonates (JAs) are a group of plant hormones which help regulate plant growth and development. Jasmonates include jasmonic acid and its esters, such as methyl jasmonate (MeJa). Like the related prostaglandin hormones found in mammals, the jasmonates are cyclopentanone derivatives which are derived biosynthetically from fatty acids. They are biosynthesized from linolenic acid by the octadecanoid pathway.

The level of JA in plants varies as a function of tissue and cell type, developmental stage, and in response to several different environmental stimuli.Creelman RA and Mullet ME. 1997. Biosynthesis and action of jasmonsates in plants. "Annual Review of Plant Physiology and Plant Molecular Biology" 48: 355-381] High levels of JA are also found in flowers and pericarp tissues of developing reproductive structures and in the chloroplasts of illuminated plants; JA levels also increase rapidly in response to mechanical perturbations such as tendril coiling and when plants suffer wounding. [Falkenstein E et al. 1991. Methyljasmonate and α-linolenic acid are potent inducers of tendril coiling. "Planta" 185: 316– 22] [Creelman RA etal. 1992. Jasmonic acid/methyl jasmonate accumulate in wounded soybean hypocotyls and modulate wound gene expression. "Proc. Natl. Acad. Sci. USA" 89:4938– 41]

Demonstrated roles of JA in planta include:
*JA and MeJA inhibit the germination of nondormant seeds and stimulate the germination of dormant seeds
*High levels of JA encourage the accumulation of storage proteins; genes encoding vegetative storage proteins are JA responsive and tuberonic acid (a JA derivative) has been proposed to play a role in the formation of tubers [Anderson JM. 1988. Jasmonic acid-dependent increases in the level of specific polypeptides in soybean suspension cultures and seedlings. "Journal of Plant Growth and Regulation". 7: 203– 11] [Pelacho AM and Mingo-Castel AM. 1991. Jasmonic acid induces tuberization of potato stolons cultured in vitro. "Plant Physiology" 97: 1253– 55]
*JA application can induce chlorosis and inhibition of genes encoding proteins involved in photosynthesis, although the purpose of this response is unknown it is proposed that this response to JA could help reduce the plant's capacity for carbon assimilation under conditions of excess light or carbon
*The role of JA accumulation in flowers and fruit is unknown; however, it may be related to fruit ripening (via ethylene), fruit carotenoid composition, and expression of genes encoding seed and vegetative storage proteins
*JA plays a role in insect and disease resistance. Many genes during plant defense are induced by JA; JA and ethylene may act together in defense response [Xu Y et al. 1994. Plant defense genes are synergistically induced by ethylene and methyl jasmonate. "Plant Cell" 6: 1077– 85]

The perception of jasmonate is via the ubiquitin system, like auxins. After the conjugation of jasmonate and an amino acid isoleucine, it led to the SCF^COI1 complex degrade the ubiquitin markerd JAZ protein, and then releasing the transcription of other transcription factors. [cite journal |author=Farmer EE |year=2007 |title=Plant biology: jasmonate perception machines |journal=Nature |volume=448 |pages=659–660 |doi=10.1038/448659a]

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