Endophytes type of interaction between an endophyte and plant

Endophytes are organisms often fungi and
bacteria that live between living plant cells. Endophytic fungus is an
endosymbiont that live within a plant for least part of his life without
causing apparent harm. These are relatively unexplored producers of metabolites
useful to pharmaceutical and agricultural industries (Petrini et al., 1992). Endophytic
fungi are ubiquitos and have been found in all species of plant (Arnold et al.,
2000). Some strains of the same fungus isolated from different parts of the
same host differ in their ability to utilize different substances (Corell and
Petrini, 1983). So, endophytes can be isolated from different plants belongs to
the different families and classes and grow under different ecological and
geographical conditions (Petrini et al., 1986). The type of interaction between
an endophyte and plant is controlled by the genes of both organism and
modulated by environment (Moricca and Ragazzi, 2008).

Endophytic fungi is separated into four
classes based on host range,type of tissue(s) colonize, colonization in planta,
diversity in planta, transmission and fitness benefits (Rodriguez et al.,

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Clavicipitaecous endophytes
are class 1 endophytes which represents a small number of phylogenetically
related Clavicipitaecous species. They are fastidious in culture and
limited to some cool and warm season grasses (Stone et al., 2004; Bischoff et al.,

Class II endophytes comprise a diversity
of species, all of which are members of the Dikarya(Ascomycota or
Basidiomycota). They have ability to confer adaptation specific stress
tolerance to hosts plants (Rodriguez et al., 2008).

Class III endophytes are differentiated
on the basis of their occurrence and transmission. This includes vascular,
nonvascular plants, woody and herbaceous angiosperm of Antarctic communities
(Davis and Shaw, 2008; Higgins et al.,
2007). They are especially known for their diversity within individual host
tissues, plants and population.

Class IV endophytes have darkly
melanized septa and are restricted to plant roots. They are generally Ascomycetous
fungi which are conidial or sterile and that form melanized structures like
inter and intracellular hyphae and also microsclerotia in the roots. This class
of endophytes found in host plants like nonmycorrizal from Antarctic, alpine, sub
alpine temperate zones and tropical ecosystem (Jumpponen, 2001).

Endophytic fungi have been considered as
possible useful sources of natural products and can protect plants from insect
attack and diseases and are also able to produce substances of biotechnological
importance(Borges et al., 2007;
Newman and Cragg, 2007; Strobel et al.,
2004). Some species of endophytic fungi have been identified as sources of
anticancer, antidiabetic, insecticidal and immunosuppressive compounds(Strobel
and Daisy, 2003). Some of them may produce secondary metabolites with potential
for antimicrobial and anticancer property (Shu et al., 2005; Xu et al.,
2008). Fusarium oxysporum has
been  isolated as endophyte
from medicinal plants with anticancer and antimicrobial activity (Xu et al., 2008).Other reports have also
showed that certain endophyic fungi produced more metabolites similar to those
produced by host plant with therapeutic function including alkaloids, steroids,
terpenoids, flavinoids, quinines, peptides and phenolic acid (Shu et al., 2005; Strobel, 2003).