Changes in cell wall polysaccharides composition of Glycine max cotyledon induced by seed attack of Sting bug Nezara viridula

MARINA CIANCIA; FRANCO ARIAS; NATALIA ILINA; EDUARDO PAGANO; JORGE ZAVALA

Barcelona

Simposio; 19th European Carbohydrate Symposium; 2017

European Carbohydrate Association

CHANGES IN CELL WALL POLYSACCHARIDES COMPOSITION OFGLYCINE MAX COTYLEDON INDUCED BY SEED ATTACK OFSTING BUG NEZARA VIRIDULAFranco A. Arias1, Natalia Ilina 1, Eduardo Pagano1, Jorge A. Zavala1,2, Marina Ciancia1,31 Universidad de Buenos Aires, Facultad de Agronomía, Buenos Aires, Argentina2CONICET-UBA. INBA, Buenos Aires, Argentina3CONICET-UBA. CIHIDECAR, Buenos Aires, Argentinae-mail: ciancia@agro.uba.arThe stink bug Nezara viridula is a serious invasive pest of agriculture, as consequence of tissuedamage they produce, and its toxic oral secretion generates economic losses in soybean (Glycinemax) crop. Plants respond to insect attack, triggering mitogen activated protein kinases (MAPK)pathway and inducing defenses against herbivores, between them, an early increase of salicylicacid (SA), which continued increasing up to 72 h after damage. In addition, induced seeds wereless preferred by stink bug [1]. The aim of this work was to determine if these changes produce ameasurable difference in the cell wall composition of seeds cotyledon. For this purpose, soybeanseeds from the commercial cultivar Williams 82 (PI 518671) were grown at experimental field.One untreated (CTR) lot, and two different treatments were performed: (1) stink bug damage (BD)? insects were placed on pods and enclosed with a fine mesh bag during 14 days; (2) pods sprayedwith 1.5mM of salicylic acid (SA) every 4/5 days for 14 days. Besides, soybean seeds transcriptswere analyzed by traditional reverse transcriptase-PCR, and it was found that stink bug attack ledto an increase in expansine (EXP), xyloglucan endo-transferase (EXT), polygalacturonase (PG) andpectate lyase (PL) genes expression at 72 h. Interestingly, when SA was applied there was a stronginduction of the same enzyme transcripts. Seeds cotyledons were sequentially extracted andextracts were purified. Their composition was determined, and some structural features wereinvestigated by methylation analysis and NMR spectroscopy. As expected, major amounts ofpectic material were obtained in all the extracts, comprising important quantities ofarabinogalactans, with predominance of 4-linked b-D-galactopyranose units, and terminal and 5-linked a-L-arabinofuranose units. The major differences between treatments were found in theextracts obtained with water and with CDTA, mainly in the amounts and degree of methylesterification (DM) of the uronic acids (UA): When comparing BG with CTR, the major differencewas found in the DM of the extract obtained with CDTA (18.0 ± 1.9 % vs 6.5 ± 2.1%,respectively). On the other hand, comparison of SA vs CTR showed ~ three times higher amountsof uronic acids in the water extract, with lower DM (9.4± 2.0 % UA with 43.0 ± 1.2 % DM, forSA, while CTR gave 3.6 ± 0.1% UA, with 100 ± 4.8 % DM), while for the extract obtained withCDTA, lower %UA was found, but with similar DM (5.4± 0.2 % UA with 4.2 ± 1.1 % DM, forSA, while CTR gave 15.3 ± 0.4% UA, with 6.5 ± 2.1 % DM). Smaller differences were alsoobserved in the neutral monosaccharides composition. These results suggest that treatmentsproduced some changes in the cell wall composition, but these changes are not the same. Analysesof extracts obtained with alkaline aqueous solutions were significant in yields, but they did notshow important differences among treatments. Our results show some evidences that stink bugdamage elicits a plant self-protection response that could involve cell wall rearrangement.[1]Giacometti, R., Barneto, J., Barriga, L.G., Sardoy, P.M., Balestrasse, K., Andrade, A.M., Pagano, E.A.,Alemano, S.G., Zavala, J.A. Early perception of stink bug damage in developing seeds of field-grownsoybean induces chemical defenses and reduces bug attack. Pest Manag Sci 2016, 72, 1585?1594