Syringolin, a Novel Peptide Elicitor from Pseudomonas syringae pv. syringae that Induces Resistance to Pyricularia oryzae in Rice

Abstract

Recognition by rice plants (Oryza sativa) of the nonhost pathogen Pseudomonas syringae pv. syringae leads to an active response ultimately resulting in local acquired resistance against the rice blast fungus Pyricularia oryzae. An observable aspect of this defense response is the increased abundance of a set of transcripts. The accumulation of one of these transcripts, Pir7b, was dependent on the function of the bacterial lemA gene, which encodes part of a twocomponent regulatory system. This suggested that the lemA regulatory system controlled the production of an elicitor of Pir7b transcript accumulation. This elicitor, which we name syringolin, was purified to homogeneity and its structure was elucidated. Syringolin is a novel and unusual secreted peptide consisting of a 12-membered ring formed by the two non-proteinogenic amino acids 5methyl-4-amino-2-hexenoic acid and 3,4-dehydrolysine. The α-amino group of the latter is connected by a peptide bond to a valine that in turn is linked to a second valine via a urea moiety. Application of syringolin onto rice leaves elicited the accumulation of Pir7b as well as of other defense-related transcripts and induced resistance toward P. oryzae. Thus, syringolin is one of several determinants by which rice plants can perceive the nonhost pathogen P. syringae pv. syringae.

Synthetic and structural studies on syringolin A and B reveal critical determinants of selectivity and potency of proteasome inhibition

“…As expected from the X-ray analysis of SylA in complex with the yeast 20S proteasome (15), the free carboxylic acid moiety is not required for potent inhibition because both SylA and SylA methyl ester (18 , Table 1) inhibit all proteolytic activities of the proteasome in a similar range. After this positive result, we started the synthesis of a suitable modified SylA derivative 21 ( Fig.…”

“…Comparison of the spectral (SI Appendix) and inhibition data (Table 1) and a coinjection experiment of synthetic and natural SylA isolated as described in ref. 18 on a chiral HPLC system indicate that our original stereochemical assignment of 1 is correct.…”

“…They exhibit an ␣,␤-unsaturated carbonyl system located within a macrocycle that reacts irreversibly with the proteasomal active site Thr1O ␥ by a Michael-type 1,4-addition. The class of syrbactins represents a collective term for two structurally closely related, nevertheless distinct natural product families: the syringolins (18,19) and the glidobactins (20).…”

Syringolin A: Action on Plants, Regulation of Biosynthesis and Phylogenetic Occurrence of Structurally Related Compounds

“…syringae in planta or when grown under conditions mimicking an in planta environment (Wäspi et al, 1998;Wäspi et al, 1999). Syringolin A has no toxic activity towards fungi and bacteria as far as tested (Wäspi et al, 1998).…”

Activity Enhancement of the Synthetic Syrbactin Proteasome Inhibitor Hybrid and Biological Evaluation in Tumor Cells

“…syringae (Pss) (1), the structurally-related glidobactins were discovered in the 1980's from an unknown species of the order Burkholderiales (2)(3)(4)(5). Syringolin A (SylA) and glidobactin A (GlbA) represent the predominant forms in these bacterial pathogens, whereas SylB-F and GlbB-F are naturally occurring syrbactin variants expressed in minor quantities (1,6,7).…”