ABSTRACT
A field-collected Aphis gossypii clone [Kushima resistant (KR) clone] was resistant to neonicotinoid insecticides (23.8- to 394-fold). RNA-seq and next-generation sequence analyses were conducted to identify nine cytochrome P450 (CYP) genes that were significantly upregulated in the KR clone as compared with those in the insecticide-susceptible clone. A. gossypii P450s were transiently and efficiently expressed in S2 cell to show that CYP6CY22 (c21228) and CYP6CY13 (c21368), which were the most upregulated of the nine P450s in the KR clone, did not degrade sulfoxaflor, a new class of insecticides acting on insect nAChRs, but markedly metabolized all of the neonicotinoids tested. Hence, P450s are likely to underpin neonicotinoid resistance in other aphids as well in the future, and the P450 expression protocol established here will prompt studies on P450-medidated insecticide resistance and structural analyses of relevant metabolites.
ABSTRACT
We prepared 19 amino acid conjugates of the plant hormone abscisic acid (ABA) and investigated their biological activity, enzymatic hydrolysis by a recombinant Arabidopsis amidohydrolases GST-ILR1 and GST-IAR3, and metabolic fate in rice seedlings. Different sets of ABA-amino acids induced ABA-like responses in different plants. Some ABA-amino acids, including some that were active in bioassays, were hydrolyzed by recombinant Arabidopsis GST-IAR3, although GST-ILR1 did not show hydrolysis activity for any of the ABA-amino acids. ABA-L-Ala, which was active in all the bioassays, an Arabidopsis seed germination, spinach seed germination, and rice seedling elongation assays, except in a lettuce seed germination assay and was hydrolyzed by GST-IAR3, was hydrolyzed to free ABA in rice seedlings. These findings suggest that some plant amidohydrolases hydrolyze some ABA-amino acid conjugates. Because our study indicates the possibility that different plants have hydrolyzing activity toward different ABA-amino acids, an ABA-amino acid may function as a species-selective pro-hormone of ABA.
Subject(s)
Abscisic Acid , Amino Acids , Abscisic Acid/chemical synthesis , Abscisic Acid/chemistry , Abscisic Acid/metabolism , Abscisic Acid/pharmacology , Amino Acids/chemical synthesis , Amino Acids/chemistry , Amino Acids/metabolism , Amino Acids/pharmacology , Arabidopsis Proteins/metabolism , Germination , Inhibitory Concentration 50 , Molecular Structure , Oryza/metabolism , Plant Growth Regulators/chemistry , Plant Growth Regulators/metabolism , Seeds/growth & development , Spectrometry, Mass, Electrospray IonizationABSTRACT
To examine the effect of the minor abscisic acid (ABA) metabolite 7'-hydroxy-ABA on Arabidopsis ABA 8'-hydroxylase (CYP707A3), we developed a novel and facile, four-step synthesis of 7'-hydroxy-ABA from alpha-ionone. Structural analogues of 7'-hydroxy-ABA, 1'-deoxy-7'-hydroxy-ABA, and 7'-oxo-ABA were also synthesized to evaluate the role of the 7'-hydroxyl group on binding to the enzyme. The result of enzyme inhibition assay suggests that the local polarity at C-7', neither steric bulkiness nor overall molecular hydrophilicity, would be the major reason why (+)-7'-hydroxy-ABA is not a potent inhibitor of CYP707A3.
