Premium
Potential involvement of A spergillus flavus laccases in peanut invasion at low water potential
Author(s) -
Arias R. S.,
Sobolev V. S.,
Orner V. A.,
Dang P. M.,
Lamb M. C.
Publication year - 2014
Publication title -
plant pathology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.928
H-Index - 85
eISSN - 1365-3059
pISSN - 0032-0862
DOI - 10.1111/ppa.12088
Subject(s) - aspergillus flavus , aflatoxin , laccase , biology , botany , food science , horticulture , biochemistry , enzyme
A spergillus flavus accumulates carcinogenic aflatoxins in peanuts, mainly in immature kernels during drought. A spergillus flavus invasion induces accumulation of phytoalexins, mostly stilbenoids in peanut, as a plant defence mechanism. Because fungal laccases are often related to pathogenicity and can degrade stilbenoids, this study reports for the first time the expression of A . flavus laccases in the presence of kernels, hulls and low water potential in relation to the accumulation of phytoalexins in peanut kernels. Packed‐cell volume ( PCV ) of A . flavu s biomass was significantly higher ( P ≤ 0·01) in the presence of mature kernels, dead kernels, and mature and immature peanut hulls than the control. The presence of kernels and hulls lowered the level of expression of three A . flavus laccases by 4–6‐fold ( P < 0·01), whereas 3% sucrose up‐regulated them by 35–304‐fold, and low water potential (−1·1 MPa) up‐regulated them by 85–248‐fold ( P < 0·01). Phytoalexins that accumulated in peanut kernels in the presence of A . flavus and were quantified by HPLC ‐ DAD ‐ MS were primarily the stilbenoids: 3′‐isopentadienyl‐3,5,4′‐trihydroxystilbene ( IPD ), chiricanine‐ A , arachidin‐2, arachidin‐3 and arahypin‐1. Apparent degradation of phytoalexins was observed when using a priori induction of phytoalexins in seeds in combination with a priori induction of laccases in A . flavus . The up‐regulation of laccase expression observed at −1·1 MPa and at high sucrose concentration could be contributing to peanut invasion in immature kernels under drought conditions.