Mitogen-Activated Protein Kinase Cascades in Plant Innate Immunity - PAMP Signals in Plant Innate Immunity: Signal Perception and Transduction - page 335

of S . sclerotiorum and constitutively activated PDF1.2 , the gene activated by JA
signaling (Wang et al. 2009 ). The results suggest that BnMPK4 positively regulates
JA-mediated defense response, which might play an important role in resistance to
S . sclerotiorum in oilseed rape.

7.2.8 Cotton GhMPK2 Are Involved in Ethylene

Biosynthesis - Mediated Plant Immune Responses

A MAPK gene, GhMPK2 , has been cloned from cotton and characterized.
Transgenic tobacco plants overexpressing GhMPK2 showed enhanced resistance to
fungal and viral pathogens (Zhang et al. 2011 ). The transgenic plants showed
enhanced expression of genes encoding ACC synthase (ACS) and ACC oxidase
(ACO), which are involved in biosynthesis of ethylene. The expression of PR genes,
PR1 , PR2 , PR4 , and PR5 , was upregulated in the transgenic plants expressing the
MAPK gene (Zhang et al. 2011 ). The results suggest that the cotton MPK2 plays an
important role in innate immune system.

7.2.9 Cotton GhMPK7 Triggers SA Signaling System

The MPK7 gene from cotton, GhMPK7 , has been found to have a role in activat-
ing defense responses in plants. Transgenic Nicotiana benthamiana plants
overexpressing GhMPK7 showed broad-spectrum disease resistance. The trans-
genic plants displayed signifi cant resistance against Colletotrichum nicotianae
and Potato virus Y (Shi et al. 2010 ). The GhMPK7 transcript was induced by
pathogen infection and also by different defense-related signal molecules.
Overexpression of the cotton MAPK gene in N . benthamiana induced rapid and
strong expression of SA pathway genes (Shi et al. 2010 ). The results suggest
that the GhMPK7 plays an important role in triggering SA signaling pathway in
plant innate immunity.

7.2.10 GhMPK16 Activates ROS-Mediated Signaling System

GhMPK16 gene has been cloned from cotton and characterized. It showed high
homology to Arabidopsis AtMPK16 . The gene transcripts have been shown to
accumulate following pathogen infection and treatment with several defense-related
signal molecules (Shi et al. 2011 ). Transgenic Arabidopsis plants overexpressing
GhMPK16 showed enhanced resistance against the fungal pathogens Colletotrichum
nicotianae and Alternaria alternata and also against the bacterial pathogen