Expression of Genes Encoding Manganese Peroxidase and Laccase of Ganoderma boninense in Response to Nitrogen Sources, Hydrogen Peroxide and Phytohormones.

Pei-Yin Ho,Shamala Sundram,Chai-Ling Ho,Parameswari Namasivayam

doi:10.3390/genes11111263

Abstract

Ganoderma produces lignolytic enzymes that can degrade the lignin component of plant cell walls, causing basal stem rot to oil palms. Nitrogen sources may affect plant tolerance to root pathogens while hydrogen peroxide (H2O2), salicylic acid (SA) and jasmonic acid (JA) play important roles in plant defense against pathogens. In this study, we examined the expression of genes encoding manganese peroxidase (MnP) and laccase (Lac) in Ganoderma boninense treated with different nitrogen sources (ammonium nitrate, ammonium sulphate, sodium nitrate and potassium nitrate), JA, SA and H2O2. Transcripts encoding MnP and Lac were cloned from G. boninense. Of the three GbMnP genes, GbMnP_U6011 was up-regulated by all nitrogen sources examined and H2O2 but was down-regulated by JA. The expression of GbMnP_U87 was only up-regulated by JA while GbMnP_35959 was up-regulated by ammonium nitrate but suppressed by sodium nitrate and down-regulated by H2O2. Among the three GbLac genes examined, GbLac_U90667 was up-regulated by ammonium nitrate, JA, SA and H2O2; GbLac_U36023 was up-regulated by JA and H2O2 while GbLac_U30636 was up-regulated by SA but suppressed by ammonium sulphate, sodium nitrate, JA and H2O2. Differential expression of these genes may be required by their different functional roles in G. boninense.

Highlights

Palm oil production is threatened by a fungal disease known as basal stem rot (BSR) which is mainly caused by Ganoderma boninense
Since G. boninense is a white rot fungus which can degrade lignin, it is crucial to investigate the regulation of genes encoding lignolytic enzymes that contribute to BSR
The transcript sequences for GbMnP and GbLac, that were previously found to be present in infected oil palm [15], were successfully isolated by rapid amplification of cDNA ends (RACE)-PCR

Summary

Introduction

Palm oil production is threatened by a fungal disease known as basal stem rot (BSR) which is mainly caused by Ganoderma boninense. Infected oil palms may not show obvious symptoms at the initial stage of infection. Ganoderma species are white rot fungi which can degrade lignin by producing extracellular ligninolytic enzymes including manganese peroxidase (MnPs; EC 1.11.1.13) and laccase (Lac; EC 1.10.3.2) [2,3]. MnP oxidizes Mn2+ to Mn3+ and nonphenolic aromatic compounds with high oxidation-reduction potentials such as lignin [4]. Lac, which is catalyzed by the redox ability of copper ions, can oxidize nonphenolic substrates with high oxidation-reduction potentials, concomitantly with the reduction of oxygen to water [5,6,7]. Purified and well characterized Lac enzymes from different Ganoderma strains have been

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Conclusion