Two O-Linked N-Acetylglucosamine Transferase Genes of Arabidopsis thaliana L. Heynh. Have Overlapping Functions Necessary for Gamete and Seed Development

Abstract

The Arabidopsis SECRET AGENT (SEC) and SPINDLY (SPY) proteins are similar to animal O-linked N-acetylglucosamine transferases (OGTs). OGTs catalyze the transfer of N-acetylglucosamine (GlcNAc) from UDP-GlcNAc to Ser/Thr residues of proteins. In animals, O-GlcNAcylation has been shown to affect protein activity, stability, and/or localization. SEC protein expressed in Escherichia coli had autocatalytic OGT activity. To determine the function of SEC in plants, two tDNA insertional mutants were identified and analyzed. Although sec mutant plants did not exhibit obvious phenotypes, sec and spy mutations had a synthetic lethal interaction. This lethality was incompletely penetrant in gametes and completely penetrant postfertilization. The rate of both female and male sec spy gamete transmission was higher in plants heterozygous for both mutations than in plants heterozygous for sec and homozygous for spy. Double-mutant embryos aborted at various stages of development and no double-mutant seedlings were obtained. These results indicate that OGT activity is required during gametogenesis and embryogenesis with lethality occurring when parentally derived SEC, SPY, and/or O-GlcNAcylated proteins become limiting.

Interference of Arabidopsis N-Acetylglucosamine-1-P Uridylyltransferase Expression Impairs Protein N-Glycosylation and Induces ABA-Mediated Salt Sensitivity During Seed Germination and Early Seedling Development

“…O-GlcNAcylation is a single O-linked GlcNAc that is attached to the serine or threonine of the cytosolic and nuclear proteins, which are involved in many aspects of cellular processes, including transcription and translation regulation, signal transduction, metabolism, and development ( Xu et al, 2017 ). When Arabidopsis SECRET AGENT (SEC), an O-GlcNAc transferase, loses functionality, multiple hormonal signaling pathways and plant growth and development, such as flowering, are affected through the impairment of O-GlcNAcylation of proteins, such as DELLA proteins, AtACINUS, AtPININ, and ARABIDOPSIS OF TRITHORAXI (ATX1), a histone lysine methyltransferase (HKMT; Hartweck et al, 2002 ; Zentella et al, 2016 ; Xing et al, 2018 ; Bi et al, 2021 ). Defects in O-GlcNAcylation homeostasis in mammals have been reported to be associated with diabetes, cancers, neurodegeneration, and even lethality ( Marshall et al, 1991 ; McClain, 2002 ; Schimmelpfeng et al, 2006 ; Hanover et al, 2010 ; Slawson et al, 2010 ; Yang and Qian, 2017 ).…”

Sweet Modifications Modulate Plant Development

“…The significance of the relation between O-GlcNAcylation and plant development, combined with signaling of GAs, was illustrated when SECRET AGENT (SEC), an O-GlcNAc transferase (OGT) from Arabidopsis, was knocked out in combination with spy. Mutant spy-sec plants carried inviable seeds [90,151,258].…”

“…O-fucosylation also affects leaf morphology such as the reduction in leaf serration size and decreased number of leaf serrations. Moreover, leaf growth was also impaired [151,154,255]. Aberrant phenotypes due to the mutation of SPY in Arabidopsis can be attributed to alterations in plant hormone responses.…”

O-fucosylation of CPN20 by SPINDLY Derepresses Abscisic Acid Signaling During Seed Germination and Seedling Development

“…In contrast, SPY was recently demonstrated to be an O-fucosyltransferase that O-fucosylates the DELLA protein, resistance gene analog (RGA) (Zentella et al, 2017). SPY, as a O-fucosyltransferase, plays an opposite role in regulating DELLA (Zentella et al, 2016(Zentella et al, , 2017Camut et al, 2017) to SECRET AGENT (SEC), the sole putative Arabidopsis OGT, with sequence and structure similarities to SPY (Hartweck et al, 2002(Hartweck et al, , 2006. Very recently, nuclear SPY was shown to facilitate PSEUDO-RESPONSE REGULATOR 5 (PRR5) proteolysis via its O-fucosylation to modulate Arabidopsis circadian clock (Wang et al, 2020).…”