Type II arabinogalactans initiated by hydroxyproline‐O‐galactosyltransferases play important roles in pollen–pistil interactions

Abstract

SUMMARY Arabinogalactan‐proteins (AGPs) are hydroxyproline‐rich glycoproteins containing a high sugar content and are widely distributed in the plant kingdom. AGPs have long been suggested to play important roles in sexual plant reproduction. The synthesis of their complex carbohydrates is initiated by a family of hydroxyproline galactosyltransferase (Hyp‐GALT) enzymes which add the first galactose to Hyp residues in the protein backbone. Eight Hyp‐GALT enzymes have been identified so far, and in the present work a mutant affecting five of these enzymes (galt2galt5galt7galt8galt9) was analyzed regarding the reproductive process. The galt25789 mutant presented a low seed set, and reciprocal crosses indicated a significant female gametophytic contribution to this mutant phenotype. Mutant ovules revealed abnormal callose accumulation inside the embryo sac and integument defects at the micropylar region culminating in defects in pollen tube reception. In addition, immunolocalization and biochemical analyses allowed the detection of a reduction in the amount of glucuronic acid in mutant ovary AGPs. Dramatically low amounts of high‐molecular‐weight Hyp‐O‐glycosides obtained following size exclusion chromatography of base‐hydrolyzed mutant AGPs compared to the wild type indicated the presence of underglycosylated AGPs in the galt25789 mutant, while the monosaccharide composition of these Hyp‐O‐glycosides displayed no significant changes compared to the wild‐type Hyp‐O‐glycosides. The present work demonstrates the functional importance of the carbohydrate moieties of AGPs in ovule development and pollen–pistil interactions.

Identification and Analysis of Candidate Genes Associated with Yield Structure Traits and Maize Yield Using Next-Generation Sequencing Technology

“…According to our analyses and data in the literature, this gene may be related to the yield of maize because, according to Kaur et al (2023), hydroxyproline o-galactosyltransferase galt6 plays an important role in various stages of plant growth and development [73]. Moreira et al (2023) have reported that arabinogalactan proteins (AGPs) are hydroxyproline-rich, sugar-rich glycoproteins widely distributed in the plant kingdom [74]. The synthesis of their complex carbohydrates is initiated by a family of hydroxyproline galactosyltransferase (Hyp-GALT) enzymes, which add the first galactose to Hyp residues in the protein backbone.…”

The plant cell wall—dynamic, strong, and adaptable—is a natural shapeshifter

“…A key area of research for the future is to understand how different AGPs and other HRGPs interact in the wall with each other and with carbohydrates, lignin, and proteins, and in those cases where the AGPs are direct signaling molecules to identify their ligand and receptor/co-receptor partners and signaling pathways. Physiological roles for some of the AGPs are just now being identified through molecular genetic analyses of biosynthetic mutants (reviewed in Moreira et al 2023 ).…”

Transcriptomic landscape ofseedstickinArabidopsis thalianafuniculus after fertilisation

“…The most inhibitory process in stk transcriptome was the glycoside catabolic process (GO:0016139). Glycosides are a wide range group of plant secondary metabolites with multifaceted roles in regulating growth, defense and reproduction in plants (Choi et al ., 2014; Kytidou et al ., 2020; Moreira et al ., 2023). Glycoside hydrolases are a family of enzymes responsible for the removal of specific sugar moieties from glycosides.…”