Biotic and Abiotic Stress-Related Expression of 1-Aminocyclopropane-l-carboxylate Oxidase Gene Family in Nicotiana glutinosa L.

Abstract

Three full length 1-aminocyclopropane-1-carboxylate (ACC) oxidase cDNA clones (pNG-ACO1, 1,254 bp; pNG-ACO2, 1,198 bp; and pNG-ACO3, 1,053 bp) were isolated from the TMV-treated leaf cDNA library of Nicotiana glutinosa plant. They share a high degree of sequence identity (78-81%) throughout the coding regions but are divergent within the 3'-untranslated regions. The gene-specific probes were prepared using these regions to investigate the differential expression of the ACC oxidase gene family in various organs and in response to a multitude of biotic and abiotic stresses in N. glutinosa plants. All three genes were transcriptionally active displaying unique patterns of expression. Both the pNG-ACO1 and pNG-ACO3 transcripts highly accumulated during the senescence of leaves, while the pNG-ACO2 mRNA was constitutively present. In addition, the NG-ACO1 and NG-ACO3 transcripts were predominantly found in roots whereas the NG-ACO2 mRNA was mainly in stems. Upon TMV infection, both NG-ACO1 and NG-ACO3 were markedly induced, but in mock treatment which has an effect of mild wounding, only the NG-ACO3 gene was induced. Furthermore, salicylic acid and CuSO4 treatments of leaves increased the level of NG-ACO1 and NG-ACO3 transcripts, while they did not affect the NG-ACO2 gene expression. Results showed that both the NG-ACO1 and NG-ACO3 genes were highly inducible by ethylene and methyl jasmonate treatments, with NG-ACO3 being more responsive. By contrast, NG-ACO2 did not respond to these growth regulators. Thus, it appears that there are two groups of ACC oxidase transcripts expressed in leaf tissue of N. glutinosa, either stress-induced or constitutive. The possible molecular mechanism of differential regulation of ACC oxidase gene expression and its physiological significance are discussed.

Alteration of the Alkaloid Profile in Genetically Modified Tobacco Reveals a Role of Methylenetetrahydrofolate Reductase in Nicotine N-Demethylation

“…Of the nine genes known to change expression during senescence, only two (NtACO1 and NtACO3) were induced as anticipated for the senescing plants; these genes are also known to be induced by other signals, such as wounding and viral infection (Kim et al, 1998). Therefore, the presented results taken together support the hypothesis that the highly induced expression of CYP82E4 in young green leaves of the KD lines is likely not triggered by senescing signals.…”

“…4). Leaf senescence is known to induce both ACS and ACO enzymes sharply, but the formation of ACC is often considered to be the rate-limiting step on the pathway (Kim et al, 1998;Wang et al, 2002;Lin et al, 2009). The lack of ACS induction, therefore, is consistent with the lack of increase in ethylene production in the analyzed transgenic plants.…”

“…ACS is involved in the rate-limiting step of ethylene biosynthesis from AdoMet to ACC, while ACO is involved in the oxidation of ACC to ethylene (Lin et al, 2009). In Nicotiana glutinosa, the ACO1 and ACO3 transcripts accumulate during senescence and are dramatically induced by ethylene treatment (Kim et al, 1998). The expression of ACS genes is regulated developmentally and environmentally (Kende, 1993).…”

Regulation of ethylene biosynthesis at the level of 1-aminocyclopropane-1-carboxylate oxidase (ACO) gene

“…In potato, highly increased expression of all ACO genes, in both low and high temperature was observed (Nie et al 2002). Wounding stimulated principally the transcription of some ACO paralogs: ST-ACO1 (Nie et al 2002), NG-ACO3 (Kim et al 1998), PP-ACO1 (Ruperti et al 2001), MA-ACO1 (Pan and Lou 2008). In contrast, Choudhury et al (2008b) observed that in preclimacteric banana fruit, wounding down-regulated the expression of both MA-ACS1 and MA-ACO1 genes and thus inhibited ethylene production.…”

Diverse responses of wild and cultivated tomato to BABA, oligandrin andOidium neolycopersiciinfection

“…Based on this result, the transcript levels of key enzymes involved in the ET synthesis pathway, namely ACC synthase and ACC oxidase, were determined along with quantification of the production of ET. On the basis of previous studies of different ACC synthase isoforms in Arabidopsis (Skottke et al, 2011;Li et al, 2012) and ACC synthase and oxidase in tomato (Lincoln et al, 1993;Kim et al, 1998;Cohn and Martin, 2005;Shi and Zhang, 2014;Yim et al, 2014), three candidate transcripts for each enzyme (ACS1a, ACS2, ACS6 for ACC synthase, and ACO1, ACO 1-like and ACO 4-like for ACC oxidase) with suspected roles in pathogenesis processes were selected.…”