Putative Role of a Yet Uncharacterized Protein Elicitor PeBb1 Derived from Beauveria bassiana ARSEF 2860 Strain against Myzus persicae (Homoptera: Aphididae) in Brassica rapa ssp. pekinensis

Abstract

This study reports the characterization of protein elicitor PeBb1 derived from entomopathogenic fungus Beauveria bassiana ARSEF-2860 strain and its putative role in induced systemic resistance in Brassica rapa ssp. pekinensis against green peach aphid Myzus persicae. The sequence of purified elicitor protein was matched with the genomic sequence of a hypothetical protein BBA_10269 from B. bassiana ARSEF-2860 (GenBank Accession No. XP_008603588.1). The protein-encoding gene PeBb1 contained 534 bp cDNA encoding a polypeptide of 177 amino acids with a molecular mass of 19 kDa. The recombinant elicitor protein was expressed in Escherichia coli using pET-28a (+) expression vector and induced necrosis in the leaves of tobacco. The effects of elicitor protein on aphid M. persicae was determined by applying three different concentrations of PeBb1 (i.e., 26, 35, 53 µM) on B. rapa plants at 4-leaf stage and the treated plants were exposed to newly emerged (0-6 h old) apterous adult aphids. Bioassay results showed significant (p < 0.05) sub-lethal effects of the exogenous application of PeBb1 elicitor on M. persicae. Moreover, the RT-qPCR gene expression analyses showed a significant up-regulation of most of the key genes linked to ethylene (ET)-and jasmonic acid (JA)-associated plant defense pathways in elicitor-treated plants.These results not only recommend the putative utilization of PeBb1 elicitor protein in future biological pest control strategies against phloem-feeding insect pests such as M. persicae, but also help in better comprehension of the mechanisms through which beneficial fungi trigger the induced plant resistance.

Sub-Lethal Effects of Partially Purified Protein Extracted from Beauveria bassiana (Balsamo) and Its Presumptive Role in Tomato (Lycopersicon esculentum L.) Defense against Whitefly (Bemisia tabaci Genn.)

“…These results validate the fact that herbivory by sap-sucking insects, for instance whiteflies, is more often manifested with enhanced expression levels of SA pathway-related genes [ 34 , 38 ]. Our results are in line with a recent study [ 50 ] that revealed important sub-lethal effects of the B. bassiana -derived PeBb1 protein elicitor on M. persicae on the plants of Brassica rapa concomitantly with the enhanced expression of JA and Et pathway-related genes.…”

Pest management via endophytic colonization of tobacco seedlings by the insect fungal pathogen Beauveria bassiana

“…naphthalene, with some plant compounds secreted via trichomes. Some of those plant compounds have been demonstrated to be potentially induced by endophytes, such as B. bassiana 55,56,59,69 . Furthermore, B. bassiana produces several anti‐insect or/and antimicrobial active metabolites that include tennelin, bassianin, pyridovericin, oosporein and pyridomacrolidin, 68,70 which might be also involved in the observed resistance against insects reported here.…”

“…Some of those plant compounds have been demonstrated to be potentially induced by endophytes, such as B. bassiana. 55,56,59,69 Furthermore, B. bassiana produces several anti-insect or/and antimicrobial active metabolites that include tennelin, bassianin, pyridovericin, oosporein and pyridomacrolidin, 68,70 which might be also involved in the observed resistance against insects reported here. All these possibilities could explain the distinctly increased resistance of B. bassiana-colonized tobacco seedlings against the aphids.…”

“…Our data show that B. bassiana ‐colonization in tobacco can result in increased stomatal and trichome densities, suggesting effects on respiration and carbon cycling. Some fungal endophytes secrete effectors or elicitors that stimulate phytohormone production and/or phytohormone‐mediated pathways that alter plant morphogenesis, potentially increasing plant fitness in diverse environments 55–57 . Key genes linked to SA and JA‐associated plant defense pathways were significantly upregulated in tobacco plants colonized by some of the B. bassiana strains tested, however, whether these strains produce effectors and/or elicitors remains to be determined.…”

“…Some fungal endophytes secrete effectors or elicitors that stimulate phytohormone production and/or phytohormonemediated pathways that alter plant morphogenesis, potentially increasing plant fitness in diverse environments. [55][56][57] Key genes linked to SA and JA-associated plant defense pathways were significantly upregulated in tobacco plants colonized by some of the B. bassiana strains tested, however, whether these strains produce effectors and/or elicitors remains to be determined. As both stomatal or trichome development are involved in innate immunity against infection by pathogens and may contribute to protection against insects, [58][59][60][61][62][63] the observed effects seen in these regards by selecting B. bassiana strains, can, at least in part, be accounted for by this increase.…”