IS SALICYLIC ACID INVOLVED IN PHOSPHITE INDUCED POLYAMINES UPON UV-B EXPOSURE?

LOBATO MC; MACHINANDIARENA MF; OYARBURO N; DALEO GR; OLIVIERI FP

SALTA

Congreso; Joint LV Annual SAIB Meeting and XIV PABMB Congress; 2019

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

Phosphite compounds (metallic salts of phosphorous acid) are widely used to protect plants from pathogenic oomycetes on a wide range ofhorticultural crops. Since they are nontoxic for the environment or human health, they are included as biocompatible compounds into strategies todiminish the use of toxic agrochemicals. In our lab we have observed that potassium phosphite (KPhi) has positive effects in increasing potatotolerance against various diseases, UV-B radiation, and on physiological parameters related to crop quality and yield. Several signaling pathwaysare described to participate in phosphite induced responses. However, the molecular mechanisms behind phosphite induced resistance are poorlyunderstood. In a previous work we have shown that KPhi primes the plant for an earlier and more intense response to P. infestans infection andthat salicylic acid (SA) would mediate this response. On the other hand, it has been reported that pathways triggered by UV-B radiation, have acrosstalk with other signaling routes in response to biotic stress. Polyamines (PAs) are molecules involved both in biotic and abiotic stress.Previously we have showed that PAs are part of the metabolic changes produced by KPhi in potato UV-B exposed leaves. In the present work, thesalicylic acid (SA) participation in the UV-B tolerance response induced by KPhi was analyzed. To this aim, transgenic tomato plants (NahG)deficient in SA accumulation, were treated with 1% KPhi and, 3 days later were exposed to 1 h/day of UV-B radiation (1.5 Wattm2) for 3 days.The pattern of the different polyamine (PA) accumulation was analyzed by TLC fractionation of dansylated PAs. As it was previously observedin potato plants, wild type tomato plants showed PA accumulation upon UV-B radiation in KPhi treated plants respect to non-treated ones. Thisaccumulation was not observed in transgenic plants indicating that the increase in PA by KPhi could be mediated by SA. The expression of genescorresponding to PAs biosynthesis was also analyzed. The accumulation of transcripts of ADC, ODC, SPDS, SPMS and SAMDC was evaluated3 days after KPhi and/or UV-B treatments. SPMS expression pattern correlates with its product accumulation (spermine). The other enzymesshowed a variable behavior, however, in all cases, these preliminary results, showed a decrease in the expression of these biosynthetic genes inNahG plants pretreated with KPhi an exposed to UV-B, respect to their controls.