Alterations in Nicotiana tabacum L. cv Xanthi Cell Membrane Function following Treatment with an Ethylene Biosynthesis-Inducing Endoxylanase

Abstract

An ethylene biosynthesis-inducing xylanase (EIX) produced by the fungus Trichoderma viride elicited enhanced ethylene biosynthesis and leakage of potassium and other cellular components when applied to leaf disks of tobacco (Nicotiana tabacum L. cv Xanthi). Suspension-cultured cells of Xanthi tobacco responded to EIX by rapid efflux of potassium, uptake of calcium, alkalization of the medium, inhibition of ethylene biosynthesis, and increased leakage of cellular components. EIX-treated cell suspensions released 1-aminocyclopropane-1-carboxylate (ACC) into the surrounding medium, resulting in a reduction of cellular pools of ACC. The responses of both cell suspensions and leaf disks were inhibited (50-80%) by the preincubation of the tissues with the calcium channel blocker La3". High concentrations of EGTA inhibited the alkalization of the medium by cell suspensions responding to EIX, but EGTA alone caused extensive loss of K' and ACC and inhibited ethylene biosynthesis by tobacco cells. Alterations in membrane function appear to be important in the mode of action of EIX in Xanthi cells.

Induction of defense responses in tobacco by the protein Nep1 from Fusarium oxysporum

“…The minimum amount of Nep1 required to induce cell death within 5 h was 5 ng/ml. The sensitivity of tobacco cells to Nep1 is similar to, if not greater than, their sensitivity to xylanase [19] and cryptogein [24]. Similar specific activity levels have been demonstrated for the Avr9 elicitor in Cf-9 tomato [42], the Pell 3 pectate lyase/elicitor in tobacco [43], and the host/cultivar specific toxin Tox A in wheat [7] when variations in experimental systems are taken into account.…”

“…Some of the plant responses induced by fungal elicitors include: ion fluxes across the plasma membrane, generation of AOS, changes in phosphorylation of specific proteins, transcription activation of various defense genes, induction of phytoalexin synthesis, ethylene biosynthesis, and localized cell death (hypersensitive response). The defense responses elicited by the EIX from Trichoderma 6iride have been well-characterized [18][19][20][21], and a group of small molecular weight proteins from Phytophthora species, known as elicitins, have also received considerable research attention [22][23][24]. Some of these proteins, Harpin being the most detailed [25][26][27], are capable of inducing systemic acquired resistance that protects plants against multiple diseases and even insects.…”

A Novel Plant Cysteine Protease Has a Dual Function as a Regulator of 1-Aminocyclopropane-1-Carboxylic Acid Synthase Gene Expression

“…Ethylene-Inducing Xylanase (EIX), a 22-kD protein elicitor (Dean and Anderson, 1991), elicits ethylene biosynthesis, hypersensitive response, and other defense responses in such plants as tomato (Lycopersicon esculentum) and tobacco (Nicotiana tabacum) (Bailey et al, 1992;Felix et al, 1993;Avni et al, 1994;Yano et al, 1998;Elbaz et al, 2002;Ron and Avni, 2004). The increase in ethylene biosynthesis is accompanied by the accumulation of 1-aminocyclopropane-1-carboxylic acid (ACC), an increase in extractable ACC synthase activity, and increases in Acs and ACC oxidase transcripts (Avni et al, 1994).…”

N-Acylethanolamine Signaling in Tobacco Is Mediated by a Membrane-Associated, High-Affinity Binding Protein

“…CB receptor-dependent modulation of mitogen-activated protein kinase activity occurs in several vertebrate cell types (Di Marzo, 1998a), although NAE modulation of kinase activity in plants has not yet been demonstrated. It should be noted that in tobacco, the xylanaseinduced alkalinization-response was reported not to operate in leaf discs, despite activation of several downstream characteristic defense responses (Bailey et al, 1992), suggesting that the alkalinization response may be in a pathway separate from some plant defense responses. Future work to delineate the signaling components that interact with NAE metabolism will help to more clearly define the role of NAE signaling in plant defense responses.…”

“…Xylanaseinduced alkalinization of tobacco cell suspension culture medium (Bailey et al, 1992;Felix et al, 1993) and its inhibition by NAEs (Tripathy et al, 1999) provided an easily measurable biological response for preliminary pharmacological experiments. The involvement of a NAE 14:0-binding protein in this response was explored using two CB receptor antagonists, AM 281 and SR 144528 (Rinaldi-Carmona et al, 1998).…”