Variability in Fusarium species Causing Wilt Disease in Crops: A Transcriptomic Approach to Characterize Dialogue Between Host and Pathogen - Crop Improvement: New Approaches and Modern Techniques - page 281

be the development of cereals, which can fix nitrogen significantly through their
associated N-fixing microbe partners. The cereal crops (such as rice, corn, wheat,
barley, sorghum and sugarcane) are consumed worldwide by humans and animals
and thus if the nitrogen fixing ability of microbes is controlled among these crops,
it will reap enormous financial as well as environmental benefits and the ways to
achieve these milestones are being discussed presently the world over (Charpentier
and Oldroyd 2010 ). Despite the recent progresses, we are at the beginning stages
and by looking at the current pace of progress the future research upholds great
promise and potential and these new insights will be of great value for the develop-
ment of sustainable production by utilizing new technologies.
Metatranscriptomics Approach
In Metatranscriptomics the environmental samples such as soil or water are used for
RNA extraction to analyze the gene expression in microbial communities without
their cultivation (Morales and Holben 2011 ; Simon and Daniel 2011 ). The study
of this multi-species association or interaction with the plant presents with oppor-
tunities, which will help in discovering relationships among plant-microbes with
potential impact. These metatranscriptomic studies of the whole microbial com-
munities at same time will lead to identification of new plant-microbe interactions
either beneficial or detrimental. For example, it is reported that among 150 Pseu-
domonas sp. from rhizosphere of wheat, 40 % of isolates increased the root growth
upon individual inoculation on wheat (Campbell and Greaves 1990 ). Further, the
outcome of the plant-microbe interaction can be determined by the influence of
environmental conditions such as abiotic along with biotic stresses on the physi-
ological pathways of plants. Thus, understanding of signaling processes and the
cross talk between individual pathways may allow harnessing these pathways to our
advantage for solving problems related to pathogenesis. The expression profiling of
the genes of signaling pathways have revealed that these mechanisms have protein
switches regulated by hormones (e.g. transcription factors, kinases or G-proteins)
(Memelink 2009 ; Yao et al. 2011 ; Depuyd and Hardtke 2011 ; Zhao et al. 2010 ). The
signaling responses to abiotic and biotic stresses are complicated such as the abiotic
stress-experiencing plants may channel their physiological resources for adaptation
towards such factors but in doing so these plants may become susceptible towards
attack by pathogen or herbivore (Thaler and Bostock 2004 ; Trewavas 2009 ; Hey
et al. 2010 ). The pathways which are activated through the mediation by abscisic
acid (ABA) seem to be dominant in providing protection towards abiotic stresses
and seem antagonistic to defense pathways controlled by SA (salicylic acid), JA
(jasmonic acid) and/or ET (ethylene) (Zabala et al. 2009 ; Raghavendra et al. 2010 ;
Peleg and Blumwald 2011 ). In plants under abiotic stresses such as UV radiation,
increase in ROS (reactive oxygen species) is triggered and these show resistance
against biotrophic pathogens and this response is also achieved when SA is applied
to plants (Bechtold et al. 2005 ; Kunz et al. 2008 ; Ahmad et al. 2010 ). In contrast