Journal of Pure and Applied MicrobiologyVol. 9 No. 4

Influence of Temperature on Appressorial Formation in M. grisea in Relation to cAMP-dependent PKA Activity

K. Viswanath*, Taru Sharma, P. Sinha and Mukesh Kumar

Indian Agricultural Research Institute, New Delhi, India

Received on 16 September 2015 and accepted on 13 November 2015

 

ABSTRACT

For leaf blast pathogen (Magnaporthe grisea), surface features exerted significant influence on conidial germination and appressorium formation. However, external application of cAMP was observed to nullify the difference in germination and appressorium formation due to surface effect as well as temperature influence. PKA activity was significantly higher at 29?C as compared to 22?C and at 34?C no activity detected. MPG gene expressed during appressorium formation was found to be influenced by temperature as expression level of MPG gene was almost 44 fold at 29?C and 34 times at 22?C in comparison to 16?C. ?Morphogenesis of conidial germ tube tip into appressorium was significantly reduced by external glycerol application (2.5 % or above) and germ tube continued to grow without formation of appressorium. It indicated that cAMP regulated PKA activity was associated with high endogenous glycerol concentration inside the tip cell of the germ tube for influx of water from the host surface through osmosis. Blast pathogenecity is a sequence of events regulated by action of PKA and MAPK and therefore to be modified by temperature and surface influence for free moisture availability. For future management strategy, host surface feature and impact of temperature on blast infection may be vital input as rise in CO2 and temperature level are thought to alter host-pathogen interaction under changing scenario.

Keywords : Appressorium formation, M. grisea, Pathogenicity, hydrophobicity, PKA activity.