Inhibition of auxin-induced ethylene production by salicylic acid in mung bean hypocotyls

Salicylic acid (SA), a common plant phenolic compound, influences diverse physiological and biochemical processes in plants. To gain insight into the mode of interaction between auxin, ethylene, and SA, the effect of SA on auxininduced ethylene production in mung bean hypocotyls was investigated. Auxin markedly induced ethylene production, while SA inhibited the auxin-induced ethylene synthesis in a dose-dependent manner. At 1 mM of SA, auxininduced ethylene production decreased more than 60% in hypocotyls. Results showed that the accumulation of ACC was not affected by SA during the entire period of auxin treatment, indicating that the inhibition of auxin-induced ethylene production by SA was not due to the decrease in ACC synthase activity, the rate-limiting step for ethylene biosynthesis. By contrast, SA effectively reduced not only the basal level of ACC oxidase activity but also the wound-and ethylene-induced ACC oxidase activity, the last step of ethylene production, in a dose-dependent manner. Northern and immuno blot analyses indicate that SA does not exert any inhibitory effect on the ACC oxidase gene expression, whereas it effectively inhibits both the in vivo and in vitro ACC oxidase enzyme activity, thereby abolishing auxin-induced ethylene production in mung bean hypocotyl tissue. It appears that SA inhibits ACC oxidase enzyme activity through the reversible interaction with Fe²⁺, an essential cofactor of this enzyme. These results are consistent with the notion that ethylene production is controlled by an intimate regulatory interaction between auxin and SA in mung bean hypocotyl tissue.     

Identification and characterization of three putative genes for 1-aminocyclopropane-1-carboxylate synthase from etiolated mung bean hypocotyl segments

The polymerase chain reaction (PCR) was used to produce 3 putative clones for ACC synthase from etiolated mung bean (Vigna radiata Rwilcz cv. Berken) hypocotyls. This was accomplished by utilizing genomic DNA from mung bean and degenerate primers made from information derived from highly conserved regions of ACC synthase from different plant tissues. The total length of pMAC-1, pMAC-2 and pMAC-3 are 308, 321, and 326 bp, respectively, all of which code for 68 amino acids. The introns for pMAC-1, pMAC-2 and pMAC-3 are 92, 105, and 110 bp, respectively. The degrees of homology at the DNA level for each of these clones is ca. 80% in their coding region and ca. 50% in their respective introns. This is the first report providing evidence that there are at least 3 genes for ACC synthase in etiolated mung bean.     

Calcium stimulation of ethylene production induced by 1-aminocyclopropane-1-carboxylic acid and indole-3-acetic acid

Journal of Plant Growth Regulation - Ca2+ stimulates 1-aminocyclopropane-1-carboxylic acid (ACC)- and indole-3-acetic acid (IAA)-dependent ethylene production in mung bean hypocotyls and senescing...     

Exogenous ethylene influences flower opening of cut roses (<Emphasis Type="Italic">Rosa hybrida</Emphasis>) by regulating the genes encoding ethylene biosynthesis enzymes

The purpose of this paper is to investigate the differential responses of flower opening to ethylene in two cut rose cultivars, ‘Samantha’, whose opening process is promoted, and ‘Kardinal’, whose opening process is inhibited by ethylene. Ethylene production and 1-aminocyclopropane-1-carboxylate (ACC) synthase and oxidase activities were determined first. After ethylene treatment, ethylene production, ACC synthase (ACS) and ACC oxidase (ACO) activities in petals increased and peaked at the earlier stage (stage 3) in ‘Samantha’, and they were much more dramatically enhanced and peaked at the later stage (stage 4) in ‘Kardinal’ than control during vasing. cDNA fragments of three Rh-ACSs and one Rh-ACO genes were cloned and designated as Rh-ACS1, Rh-ACS2, Rh-ACS3 and Rh-ACO1 respectively. Northern blotting analysis revealed that, among three genes of ACS, ethylene-induced expression patterns of Rh-ACS3 gene corresponded to ACS activity and ethylene production in both cultivars. A more dramatic accumulation of Rh-ACS3 mRNA was induced by ethylene in ‘Kardinal’ than that of ‘Samantha’. As an ethylene action inhibitor, STS at concentration of 0.2 mmol/L generally inhibited the expression of Rh-ACSs and Rh-ACO in both cultivars, although it induced the expression of Rh-ACS3 transiently in ‘Kardinal’. Our results suggests that ‘Kardinal’ is more sensitive to ethylene than ‘Samantha’; and the changes of Rh-ACS3 expression caused by ethylene might be related to the acceleration of flower opening in ‘Samantha’ and the inhibition in ‘Kardinal’. Additional results indicated that three Rh-ACSs genes were differentially associated with flower opening and senescence as well as wounding.