Forgotten Actors: Glycoside Hydrolases During Elongation Growth of Maize Primary Root

Abstract

Plant cell enlargement is coupled to dynamic changes in cell wall composition and properties. Such rearrangements are provided, besides the differential synthesis of individual cell wall components, by enzymes that modify polysaccharides in muro. To reveal enzymes that may contribute to these modifications and relate them to stages of elongation growth in grasses, we carried out a transcriptomic study of five zones of the primary maize root. In the initiation of elongation, significant changes occur with xyloglucan: once synthesized in the meristem, it can be linked to other polysaccharides through the action of hetero-specific xyloglucan endotransglycosidases, whose expression boosts at this stage. Later, genes for xyloglucan hydrolases are upregulated. Two different sets of enzymes capable of modifying glucuronoarabinoxylans, mainly bifunctional α-arabinofuranosidases/β-xylosidases and β-xylanases, are expressed in the maize root to treat the xylans of primary and secondary cell walls, respectively. The first set is highly pronounced in the stage of active elongation, while the second is at elongation termination. Genes encoding several glycoside hydrolases that are able to degrade mixed-linkage glucan are downregulated specifically at the active elongation. It indicates the significance of mixed-linkage glucans for the cell elongation process. The possibility that many glycoside hydrolases act as transglycosylases in muro is discussed.

Growing Maize Root: Lectins Involved in Consecutive Stages of Cell Development

“…It encodes dirigent domain-containing jacalin-related lectin that specifically interacts with maize β-glucosidase isozymes ZmBGLU1 ( Zm00001d023994 ) and ZmBGLU2 ( Zm00001d024037 ), forming large insoluble complexes [ 53 ]. ZmBGLU1 was characterized by exceptionally high expression in growing maize root; however, in contrast to BGAF1, the highest levels of ZmBGLU1 mRNA were observed in the active and late elongation zones [ 19 ]. BGAF1 was identified as a polyspecific lectin with a marked preference for Gal.…”

“…Thus, GH35 proteins and proteins containing the galactose-binding lectin domain are roughly the same. The expression of genes encoding GH35 members in the growing maize root was previously described [ 19 ]. It is important to note here that at least one of these genes belonged to the top 10 of each expression cluster ( Table 2 ).…”

“…Zones that contained cells at different stages of development were distinguished depending on the distance from the root apex: the root cap, the meristem zone (the zone of cell division), the zone of early elongation, the active elongation zone and the late elongation zone ( Figure 1 A). Plant material, RNA extraction, sequencing procedures and initial steps of transcriptomic analysis were previously described [ 18 , 19 ]. Raw data as fastq files were uploaded to the Sequence Read Archive under BioProject accession number PRJNA639682.…”

“…Maize ( Zea mays ) root tip contains cell zones at different stages of cell development that can be easily distinguished. Previously, transcriptomic data for five zones of maize root apex were published, including a comprehensive analysis of expressed genes for glycosyltransferases and glycoside hydrolases involved in cell wall metabolism [ 18 , 19 ]. The samples that were also extensively analyzed by immunocytochemistry for cell-wall-related epitopes included root cap, meristem zone, early elongation, active elongation and late elongation zones, making it possible to relate gene expression to specific early stages of root morphogenesis.…”

Elucidating the patterns of pleiotropy and its biological relevance in maize

“…All other genes within, or next to the most pleiotropic intervals, were only present in one population. In GAP field traits, xylanase/glycosyl hydrolase10 (xyn10, Zm00001d039958) has been shown to impact mesocotyl length after deep-seeding [47], with the larger family of glycoside hydrolases being involved in plant cell enlargement and composition [48]. A highly pleiotropic locus in GAP mass features included empty pericarp2 (Zm00001d005675), which is involved in embryo morphogenesis, shoot development, and the negative regulation of the heat shock response [49][50][51].…”