Biosynthesis and Defensive Function of N  Δ-Acetylornithine, a Jasmonate-Induced Arabidopsis Metabolite  

Abstract

Since research on plant interactions with herbivores and pathogens is often constrained by the analysis of already known compounds, there is a need to identify new defense-related plant metabolites. The uncommon nonprotein amino acid N d -acetylornithine was discovered in a targeted search for Arabidopsis thaliana metabolites that are strongly induced by the phytohormone methyl jasmonate (MeJA). Stable isotope labeling experiments show that, after MeJA elicitation, Arg, Pro, and Glu are converted to Orn, which is acetylated by NATA1 to produce N d -acetylornithine. MeJA-induced N d -acetylornithine accumulation occurs in all tested Arabidopsis accessions, other Arabidopsis species, Capsella rubella, and Boechera stricta, but not in less closely related Brassicaceae. Both insect feeding and Pseudomonas syringae infection increase NATA1 expression and N d -acetylornithine accumulation. NATA1 transient expression in Nicotiana tabacum and the addition of N d -acetylornithine to an artificial diet both decrease Myzus persicae (green peach aphid) reproduction, suggesting a direct toxic or deterrent effect. However, since broad metabolic changes that are induced by MeJA in wild-type Arabidopsis are attenuated in a nata1 mutant strain, there may also be indirect effects on herbivores and pathogens. In the case of P. syringae, growth on a nata1 mutant is reduced compared with wild-type Arabidopsis, but growth in vitro is unaffected by N d -acetylornithine addition.

Arabidopsis NATA1 acetylates putrescine and decreases defense-related hydrogen peroxide accumulation

“…We now provide an explanation for this observation by showing that, in addition to using Orn and diaminopropane as substrates (Adio et al, 2011;Jammes et al, 2014), NATA1 functions as a putrescine acetyltransferase (Fig. 1B).…”

“…In the case of bacteria on the leaf surface, coronatine can prevent flagellininduced stomatal closure, thereby enabling bacterial entry into the leaves (Melotto et al, 2006). Arabidopsis NATA1 (N-ACETYLTRANSFERASE ACTIVITY1; At2g39030), which is one of the most strongly induced genes after jasmonate or coronatine treatment, is an Orn acetyltransferase that produces N d -acetyl-Orn from Orn (Adio et al, 2011). The NATA2 gene (At2g39020) is directly adjacent to NATA1 in the Arabidopsis genome and encodes a protein that is 80% identical to NATA1.…”

“…The NATA2 gene (At2g39020) is directly adjacent to NATA1 in the Arabidopsis genome and encodes a protein that is 80% identical to NATA1. However, unlike NATA1, NATA2 expression is not induced by jasmonic acid or coronatine (Adio et al, 2011). Instead, NATA2 is expressed at a uniformly high level throughout Arabidopsis development (Supplemental Fig.…”

“…After infiltration into Arabidopsis leaves, virulent P. syringae DC3000 propagation was lower in nata1 mutant than in wild-type Columbia-0 (Col-0) plants (Adio et al, 2011), suggesting that NATA1 might function in suppressing antibacterial defenses. We now provide an explanation for this observation by showing that, in addition to using Orn and diaminopropane as substrates (Adio et al, 2011;Jammes et al, 2014), NATA1 functions as a putrescine acetyltransferase (Fig.…”

Pipecolic acid enhances resistance to bacterial infection and primes salicylic acid and nicotine accumulation in tobacco

“…10,11 Further, the formation of acetylated amino acids and phytohormone-amino acid conjugates can mediate or negatively regulate plant defense signaling and pathogen resistance. [12][13][14] Also, enhanced production of particular amino acids can directly impact plant resistance to specific pathogen types. For instance, analyses of Arabidopsis dmr1 with mutational defects in homoserine kinase and rsp1…”