Induction of natural defence accompanied by salicylic acid-dependant systemic acquired resistance in tomato seedlings in response to bioelicitors isolated from green algae

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• 作者：Cherkaoui El Modafar^a ; ^{elmodafar@fstg-marrakech.ac.ma} ; ^{elmodafar@ucam.ac.ma} ; Mohamed Elgadda^a ; Redouan El Boutachfaiti^b ; Elfaiza Abouraicha^a ; Naima Zehhar^a ; Emmanuel Petit^b ; Zainab El Alaoui-Talibi^a ; Bernard Courtois^b ; Josiane Courtois^b
• 关键词：Bioelicitors ; Poly- and oligosaccharides ; Ulva lactuca ; Natural defences ; Salicylic acid ; Systemic acquired resistance
• 刊名：Scientia Horticulturae
• 出版年：2012
• 期刊代码：93_03044238
• 类别：abs
• 出版时间：1 May, 2012
• 卷：138
• 期：Complete
• 页码：55-63
• 文件大小：400 K

摘要

Poly- and oligosaccharides isolated from the green algae Ulva lactuca were tested for their capacity elicitor of natural defences in tomato seedlings. After internodal infiltration of the bioelicitor solution in the midstem of tomato seedlings, the elicitor capacities were evaluated by determining the activity of phenylalanine ammonia-lyase (PAL) in the leaves located above and below the elicitation site. The results obtained showed that the crude extract of U. lactuca polysaccharides expressed an elicitor capacity of PAL activity in leaves. This expression level was similar and even higher than the ones due to other algae polysaccharides (carrageenan, laminarin and alginate). The crude extract of polysaccharides contained two polysaccharides, the glucuronan (unsulfated homopolymer) and the ulvan (sulfated heteropolymer). The glucuronan had no significant elicitor effect whereas the ulvan induced an elicitor capacity higher than that of the crude polysaccharidic extract. The desulfation of the ulvan caused a suppression of its elicitor capacity of PAL activity. The oligoulvans (sulfated 尾-螖-(4,5)-oligorhamnoglucuronans, degree of polymerization average = 2) and the oligoglucuronans (尾-螖-(4,5)-oligoglucuronans, degree of polymerization average = 3) were prepared from the ulvan and the glucuronan using two specific enzymes a ulvan lyase and a glucuronan lyase, purified from the bacterial strain Ochrobactrum sp. PEC2. The treatment of tomato seedlings with the oligoulvans was accompanied by a strong stimulation of PAL activity, reaching a maximum activity of 2-2.5 times higher than that of the ulvan polymer. Although the oligoglucuronans expressed an elicitor capacity in PAL activity twice higher than that of the glucuronan polymer, its induction was less important than the oligoulvans. The high elicitor capacity of these saccharides seemed to be related to sulfate substituents and the rhamnose residues. The stimulation of PAL activity was accompanied by an increase of phenolic compounds content and an induction of salicylic acid in the leaves located above and below the elicitation site. The treatments of tomato seedlings with U. lactuca elicitors significantly reduced wilt development caused by Fusarium oxysporum f. sp. lycopersici. The percent of wilting and mortality after 45 days was markedly reduced when plants were treated with oligoulvans, respectively 44%and 54%compared to the control plants.

The whole of these results showed clearly those U. lactuca elicitors, particularly the ulvan and the oligoulvans, induced in tomato seedlings the stimulation of natural systemic defences accompanied by a systemic acquired resistance that seems to be salicylic acid-dependent.