Induction of ethylene biosynthesis and necrosis in weed leaves by aFusarium oxysporumprotein

Abstract

A small assortment of microbial proteins have the ability to activate defense responses and induce necrosis in plant cells through cell signaling pathways. These proteins are of interest because of their potential use as bioherbicides and inducers of plant resistance in agriculture. A 24-kDa protein (Nep1) was purified from culture filtrates of Fusarium oxysporum, and the effects of this protein on weed leaves were investigated. This protein induced necrosis in detached leaves of Papaver somniferum, Lycopersicon esculentum, Malva neglecta, and Acroptilon repens when taken up through the petiole. The pattern and level of necrosis were dependent on the plant species. Treatment with Nep1 induced the production of ethylene in isolated leaves of various species, and the level of ethylene response was shown to be correlated to the concentration of the protein. Pretreating leaves of P. somniferum, L. esculentum, M. neglecta, and Cardaria draba with 100 µl L−1 ethylene enhanced the protein induction of ethylene biosynthesis in those leaves. Application of Nep1 (200 nM) as a spray to intact plants of Abutilon theophrasti, P. somniferum, Centaurea solstitialis, Centaurea maculosa, and Sonchus oleraceus resulted in extensive necrosis of leaves within 48 h. The results of this research are supplemental to our understanding of the role of specific polypeptides in plant/microbe interactions and demonstrates for the first time that a fungal protein can cause extensive necrosis when applied to weed species as a foliar spray.

The biology of Canadian weeds. 3. Lepidium draba L., L. chalepense L., L. appelianum Al-Shehbaz (updated)

“…Studies in Maryland showed that L. draba did not develop visible leaf necrosis after exposure to a microbial protein (Nep1) purified from Fusarium oxysporum Schltndl: Fr., but did respond with ethylene biosynthesis at high Nep1 concentration levels (Jennings et al 2000). The comparatively low responses of L. draba suggest that the use of Nep1 as a biologically based alternative to herbicides would be less effective than for many other weeds in the study.…”

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

“…It has been demonstrated that Nep1 causes extensive foliar necrosis when applied as a foliar spray to dicot weed species [15,16], an activity that has not been demonstrated for other necrosis inducing proteins whether toxins or elicitors. Critical to the response of plants to foliar sprays with Nep1 is the inclusion of surfactants (Silwet-L77) which appears to allow penetration of the leaf epidermal layer through stomata [15,16].…”

“…Critical to the response of plants to foliar sprays with Nep1 is the inclusion of surfactants (Silwet-L77) which appears to allow penetration of the leaf epidermal layer through stomata [15,16]. Nep1 promotes disease in at least one plantpathogen interaction [17] and is compatible with some herbicides [16].…”

“…Interestingly, it has been demonstrated for the first time that Nep1, an extra-cellular microbial protein, can be applied to many dicot weed species as a foliar spray where it causes extensive necrosis in a manner resembling the response to a contact herbicide [15]. In addition, it has been demonstrated that Nep1 remains active when co-applied with the chemical herbicides 2,4-D and glyphosate [16].…”

First evidence of ethylene production byFusarium mangiferaeassociated with mango malformation

“…2,[15][16][17][18][19][20] Biotic stress (e.g., pathogen attack) elicits ethylene synthesis in plants. 21 Ethylene production by Fusarium spp in vitro was measured under comparable conditions.…”