Differential induction of pathogenesis-related proteins in banana in response to Mycosphaerella fijiensis infection

Abstract

Black leaf streak or "black Sigatoka" is one of the most important diseases affecting bananas and plantains worldwide. Very few studies have been published on the host-pathogen interaction of this pathosystem, particularly at the molecular level. The aim of this work was to analyze, under controlled conditions, the enzyme activity of peroxidase (POX), phenylalanine ammonia lyase (PAL), β-1, 3-glucanase (GLU) and chitinase (CHI) as well as the production of H 2 O 2 in banana plants infected with Mycosphaerella fijiensis. Defence responses were examined and compared in a resistant (Calcutta 4) and a susceptible (Williams) cultivar. Plants were inoculated and tested for enzyme activity at 0, 6, 12, 18, 24, 48 and 72 h after infection (HAI) and 6, 9, 12, 15 and 18 days after inoculation (DAI). A rapid induction of PAL, POX and GLU was observed in the resistant cultivar at 6-18 HAI as well as H 2 O 2 production at 72 HAI. In contrast, in the susceptible cultivar, induction of these enzymes was only observed from 6 DAI. These results suggest that the first 72 HAI are important in determining the response of the host to the disease. Further studies characterizing banana responses to M. fijiensis at the early stages of the infection are necessary in order to better understand this host-pathogen interaction.

Phenylphenalenones protect banana plants from infection by Mycosphaerella fijiensis and are deactivated by metabolic conversion

“…; Torres et al . ). The production of defence‐related proteins could explain the reduced content of amino acids found in the infected plant tissue of both Musa varieties.…”

“…Reactive oxygen species like hydrogen peroxide, which have been reported to be produced in the infected tissue of Musa plants (Torres et al . ), could function as the oxidizing agent. In ‘Williams’, the susceptibility seemed to be associated with a late recognition of the pathogen, which then successfully colonizes the plant tissue.…”

“…Gene expression demands a substantial pool of amino acids for the synthesis of proteins commonly associated with the defence against pathogens. For example, chitinases and glucanases have been reported to play a role in the interaction between Musa and M. fijiensis and in other plant pathosystems (Harish et al 2009;Torres et al 2012). The production of defence-related proteins could explain the reduced content of amino acids found in the infected plant tissue of both Musa varieties.…”

“…For the variety 'KTR', an early response was observed by the appearance of small specks on the lower surface of the infected leaf 7-9 dpi with the fungus, regardless of which M. fijiensis strain was used; no symptoms were detectable in the variety 'Williams' up to 15-17 dpi (Table S1). This difference between varieties is not surprising because an early recognition of virulence effectors from the pathogen triggers the defence mechanism in Musa (as they do in other plant-pathogen systems), conferring resistance on plants that are attacked (Hoss et al 2000;Torres et al 2012).…”

“…Thus, several biochemical traits in Musa have been recognized to play a role during the pathogenesis. Among these, strengthened physical barriers through lignin biosynthesis, along with induction of pathogenesisrelated proteins, hypersensitivity response and production of phytoalexins, constitute the basis for the broad resistance of Musa plants to pathogens and herbivores Hölscher et al 2014;Otálvaro et al 2007;Torres et al 2012;Vaganan et al 2014;Wang et al 2015). Phenylphenalenones, a group of polycyclic aromatic compounds found in Haemodoraceae, Pontederiaceae, Strelitziaceae and Musaceae plant families (Munde et al 2013), act as phytoalexins in the Musa genus because they are induced either in the leaves or in the roots of Musa plants that are affected by biotic or abiotic factors.…”