Disease relevance of systemin

• Tomato plants (Lycopersicon esculentum, var. Better Boy) were stably transformed with a gene consisting of the open reading frame of a prosystemin cDNA under the regulation of the cauliflower mosaic virus 35S promoter [1].
• Tomato (Lycopersicon esculentum Mill.) prosystemin in fusion with a viral signal peptide was expressed in Sf21 insect cell cultures after infection with recombinant baculoviruses [2].

High impact information on systemin

• A gene that encodes systemin, a mobile 18-amino acid polypeptide inducer of proteinase inhibitor synthesis in tomato and potato leaves, has been isolated from tomato, Lycopersicon esculentum [3].
• The gene has 10 introns and 11 exons, ten of which are organized as five homologous pairs with an unrelated sequence in the eleventh, encoding systemin [3].
• Systemin is proteolytically processed from a 200-amino acid precursor protein, prosystemin [3].
• Conversely, an activator of the H+-ATPase (fusicoccin) acidified the growth medium of L. peruvianum cell cultures and suppressed systemin-induced medium alkalinization [4].
• Systemin is an important mediator of wound-induced defense gene activation in tomato plants, and it elicits a rapid alkalinization of the growth medium of cultured Lycopersicon peruvianum cells [4].

Chemical compound and disease context of systemin

• Characterization of prosystemin expressed in the baculovirus/insect cell system reveals biological activity of the systemin precursor [2].

Biological context of systemin

• Thus, this binding site exhibits the characteristics expected for a functional systemin receptor [5].
• Binding was also competed by the systemin antagonists syst1-14 and syst-Ala-17 (IC50 of 500 and 1000 nM, respectively) [5].
• Receptor-mediated tyrosine phosphorylation of a 48-kDa mitogen-activated protein kinase and alkalinization of the medium of suspension-cultured cells in response to systemin and carbohydrate elicitors were also inhibited by suramin [6].
• A transgenic line with reduced prosystemin expression showed similar susceptibility as Defenseless, whereas a prosystemin-overexpressing transgene was highly resistant [7].

Anatomical context of systemin

• The isolation to homogeneity of the 160-kDa systemin cell-surface receptor (SR160) from plasma membranes of suspension cultured cells of Lycopersicon peruvianum is reported [8].
• The activity of a protease capable of processing systemin carboxy-terminal of Lys14 was detected in tomato plasma membranes and may be responsible for the inactivation process [9].
• At the subcellular level, prosystemin was found compartmentalized in the cytosol and the nucleus of vascular parenchyma cells [10].

Associations of systemin with chemical compounds

• Tomato CP mRNA was detected within 3 h after wounding, or treatment with systemin or methyl jasmonate [11].
• To study the molecular basis of perception, we extended the C-terminal end of systemin by a tyrosine residue and radioiodinated it to yield systemin-125I-iodotyrosine [5].
• Likewise, intact systemin showed stimulatory, syst1-14 antagonistic activity, and syst15-18 showed no activity in leaf pieces of tomato (L. esculentum) plants assayed for the induction of ethylene biosynthesis [5].
• The inhibition of medium alkalinization by suramin was reversible in the presence of high concentrations of systemin and carbohydrate elicitors [6].
• The polysulfonated compound heparin did not inhibit systemin-induced medium alkalinization [6].

Regulatory relationships of systemin

• Tomato plants transformed with an antisense prosystemin complementary DNA exhibited greatly suppressed systemic wound induction of proteinase Inhibitor I and II synthesis in leaves [3].

Analytical, diagnostic and therapeutic context of systemin

• Using a radioreceptor assay, we show that suramin interfered with the binding of the systemin analog (125)I-Tyr-2, Ala-15-systemin to the systemin receptor with an IC(50) of 160 microM [6].

References