Turnover of 1-Aminocyclopropane-1-Carboxylic Acid Synthase Protein in Wounded Tomato Fruit Tissue

Abstract

Ethylene production in plant tissues declines rapidly following induction, and this decline is due to a rapid decrease in the activity of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, a key enzyme in ethylene biosynthesis. To study the nature of the rapid turnover of ACC synthase in vivo, proteins in wounded ripening tomato (Lycopersicon esculentum) fruit discs were radiolabeled with [5S]methionine, followed by a chase with nonradioactive methionine. Periodically, the radioactive ACC synthase was isolated with an immunoaffinity gel and analyzed. ACC synthase protein decayed rapidly in vivo with an apparent half-life of about 58 min. This value for protein turnover in vivo is similar to that previously reported for activity half-life in vivo and substratedependent enzyme inactivation in vitro. Carbonylcyanide-m-chlorophenylhydrazone and 2,4-dinitrophenol, potent uncouplers of oxidative phosphorylation, strongly inhibited the rapid decay of ACC synthase protein in the tissue. Degradation of this enzyme protein was moderately inhibited by the administration of aminooxyacetic acid, a competitive inhibitor of ACC synthase with respect to its substrate S-adenosyl-L-methionine, a,a'-dipyridyl, and phenylmethanesulfonyl fluoride or leupeptin, serine protease inhibitors. These results support the notion that the substrate Sadenosyl-L-methionine participates in the rapid inactivation of the enzyme in vivo and suggest that some ATP-dependent processes, such as the ubiquitin-requiring pathway, are involved in the degradation of ACC synthase proteins.

The eto1, eto2, and eto3 Mutations and Cytokinin Treatment Increase Ethylene Biosynthesis in Arabidopsis by Increasing the Stability of ACS Protein

“…The half-life of ACS in vitro in the presence of saturating concentrations of S-adenosyl-Met has been reported to be similar to that of the in vivo ACS activity (Satoh and Esashi, 1986;Satoh et al, 1993). Furthermore, the inhibition of ACS activity by either the competitive inhibitor aminooxyacetic acid or the pyridoxal inhibitor aminoethoxyvinylglycine increased the half-life of ACS enzyme activity both in vitro and in vivo (Yoshii and Imaseki, 1982;Kim and Yang, 1992) and was shown in one case to increase the half-life of the ACS protein (Kim and Yang, 1992). These data support a model in which mechanism-based inactivation of ACS is a key component of the in vivo turnover of ACS.…”

“…The half-life of ACS activity (as determined by the treatment of tissues with cycloheximide) has been reported to be 20 min in tomato leaves (Spanu et al, 1990), 25 min in mung bean hypocotyls (Yoshii and Imaseki, 1982), 40 min in tomato cell suspension cultures (Spanu et al, 1990), and 40 min and 2 h in green and pink tomato fruits, respectively (Kende and Boller, 1981). Kim and Yang (1992) examined the turnover of ACS protein (rather than activity) in tomato tissue using pulse-chase analysis and determined half-lives of 48 and 58 min in two separate experiments. This finding likely reflects an underestimation of the turnover rate (i.e., the actual halflife is likely to be shorter), because it would take some time to chase the relatively large pool of labeled Met that had accumulated in the plant cells.…”

Determining Degradation and Synthesis Rates of Arabidopsis Proteins Using the Kinetics of Progressive 15N Labeling of Two-dimensional Gel-separated Protein Spots

“…One of the five fastest K D values recorded was for the ethylene biosynthesis enzyme, ACC (1-aminocyclopropane carboxylic acid) oxidase. The rapid turnover of proteins in this pathway has been known for some time (44,45). This rapid degradation is needed to quickly slow the rate of ethylene synthesis after its peak (44), and the degradation process is actively regulated as a means of manipulating ethylene signaling in plants (46).…”

“…The rapid turnover of proteins in this pathway has been known for some time (44,45). This rapid degradation is needed to quickly slow the rate of ethylene synthesis after its peak (44), and the degradation process is actively regulated as a means of manipulating ethylene signaling in plants (46). We identified several translational initiation factors known to be responsible for initiation of programmed cell death triggered as a response to Pseudomonas syringae infection (At1g26630 FBR12) and in brassinosteroid signaling in plants (At2g46280 TRIP-1) as among the most rapidly degrading proteins.…”

Related to Ubiquitin 1 and 2 Are Redundant and Essential and Regulate Vegetative Growth, Auxin Signaling, and Ethylene Production in Arabidopsis

“…The biosynthetic pathway unique to ethylene uses the methyl donor S-adenosyl Met and consists of only two enzymes: ACS (1-aminocyclopropane-1-carboxylic acid [ACC] synthase) and ACO (ACC oxidase). ACS genes produce 10 functional proteins, some have been demonstrated to be relatively short lived (Kim and Yang, 1992) and regulated at transcriptional (Yamagami et al, 2003) and posttranslational levels (Chae et al, 2003). ACO mRNA accumulates in response to ethylene, indicating that ethylene exerts positive feed-forward regulation (Petruzzelli et al, 2000).…”