Casas, M.I., Falcone-Ferreyra, M.L., Jiang, N., Mejía-Guerra, M.K., Rodríguez, E., Wilson, T., Engelmeier, J., Casati, P., and Grotewold, E. (2016). Identification and characterization of maize salmon silks genes involved in insecticidal maysin biosynthesis. Plant Cell 28: 1297–1309.
We inadvertently added an extra -CH2- to the structures of UDP-4-keto-6-deoxy glucose and UDP-rhamnose within the structure of maysin and these other molecules, a mistake that was kindly brought to our attention by Ying Zeng (Kunming Institute of Botany, Chinese Academy of Sciences, Yunnan, China). This slightly affected Figures 1, 2A, and 5 but did not have any effect on any of the results or conclusions of the study.
For ease of comparison, the original and corrected versions of the three figures affected by this mistake are presented below with the positions of the errors and corrections marked with red arrows.
Figure 1.
Proposed 3-Deoxyflavonoid Biosynthetic Pathway.
Condensation of p-coumaroyl-CoA and malonyl-CoA by chalcone synthase (CHS; C2) results in naringenin chalcone, which is then converted to naringenin by chalcone isomerase (CHI; encoded by CHI1). Naringenin is converted to eriodictyol by a flavanone-3′-hydroxylase (F3′H1; encoded by PR1), which could then be converted to the flavone luteolin by a flavone synthase (FNS; FNSI-1) (Falcone Ferreyra et al., 2015). Eriodictyol is converted to isoorientin (C-glycosyl flavone) by a flavanone-2-hydroxylase (F2H; CYP93G5) (Morohashi et al., 2012) and a C-glucosyl transferase (CGT; UGT708A6) (Falcone Ferreyra et al., 2013). The proposed steps for conversion of isoorientin to maysin involve at least two enzymatic conversions by as yet uncharacterized enzymes. Eriodictyol is also converted to luteoforol (flavan-4-ol) by a dihydroflavonol reductase (DFR; A1) and subsequently to luteolinidin (3-deoxy anthocyanidin) by what is thought to be an ANS-like enzyme (Liu et al., 2010) or is polymerized into phlobaphenes. Enzymes identified are shown in black, and proposed steps are in gray. Phlobaphenes are shown in red, and 3-deoxyanthocyanidins are shown in pink.
Figure 2.
Biochemical Analysis of sm Lines.
(A) Proposed pathway for maysin formation. The reaction from IO to RIO is proposed to be mediated by sm2 and the dehydration of RIO to maysin (M) by sm1.
Figure 5.
Proposed Mechanism for RHS1 as sm1 Candidate.
RHS1 contains two domains characteristic of plant rhamnose synthases.
(A) The N-terminal domain between residues 20 and 262 corresponds to a NAD+-dependent dehydratase and the C-terminal domain corresponds to an epimerase/reductase between residues 389 and 652.
(B) UDP-rhamnose biosynthesis starts with a dehydration step to form the UDP-4-keto-6-deoxy glucose intermediate, which is then converted to UDP-rhamnose by an epimerization reduction step.
(C) Proposed mechanism for RHS1 involvement in maysin biosynthesis by dehydrating the glucose moiety in rhamnosylisoorientin.
Footnotes
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Editor’s note: the corrected figures and accompanying text were reviewed by members of The Plant Cell editorial board.