TITLE:
Interactions and Effects on Cysteine Synthase Activity of Aminooxyacetate and Boc-Aminooxyacetate on the Bioherbicides Colletotrichum truncatum and Alternaria cassia and Their Weed Hosts
AUTHORS:
Robert E. Hoagland, Kangetsu Hirase, C. Douglas Boyette
KEYWORDS:
Aminooxyacetate, Bioherbicide, Cysteine Synthase, Pyridoxal Phosphate Antagonist, Sicklepod, Senna obtusifolia, Hemp Sesbania, Sesbania exaltata, Transaminase
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.12 No.5,
May
26,
2021
ABSTRACT: Aminooxyacetate (AOA) is a pyridoxal phosphate
antagonist that inhibits various plant enzymes (including transaminases) which
require pyridoxal phosphate as a cofactor and it exhibits phytotoxic and
herbicidal properties. We examined AOA and its analog, N-t-butoxycarbonyl-AOA
(Boc-AOA) for phytotoxicity, interactions with weed pathogens (bioherbicides),
and effects on an important pyridoxal requiring enzyme, cysteine synthase (CS,
E.C. 4.2.99.8). Studies were performed on two weeds, i.e., hemp sesbania [Sesbania
exaltata (Raf.) Rybd. Ex A.W. Hill] and sicklepod (Senna obtusifolia), and two pathogens, (Colletotrichum truncatum and Alternaria
cassiae), that are bioherbicidal agents against hemp sesbania and
sicklepod, respectively. Pathogenicity tests, and assays for extractable, and in vitro CS activities were utilized. Phytotoxicity
bioassays indicated that the bulky t-butoxycarbonyl
moiety substitution on the AOA molecule did not substantially hinder expression
of biological activity of Boc-AOA in these tests. Generally, spray application
of the compounds to young dark-grown seedlings caused little growth effects,
but root-feeding of the chemicals reduced growth (stem elongation) in both
weeds. Hemp sesbania was generally more tolerant than sicklepod to these
compounds. The only apparent positive interaction of the chemicals with these
pathogens was the Boc-AOA: C. truncatum combination
treatment on hemp sesbania. Both compounds reduced extractable CS in the
seedlings by 30%, 72 h after treatment. CS activity was reduced by 15% in hemp
sesbania treated with C. truncatum but increased 20% above control levels after infection of sicklepod by A. cassiae. This latter effect suggests
that CS may be involved in sicklepod defense mechanisms against this pathogen.