UDP‐Api/UDP‐Xyl synthases affect plant development by controlling the content of UDP‐Api to regulate the RG‐II‐borate complex

Abstract

Rhamnogalacturonan-II (RG-II) is structurally the most complex glycan in higher plants, containing 13 different sugars and 21 distinct glycosidic linkages. Two monomeric RG-II molecules can form an RG-II-borate diester dimer through the two apiosyl (Api) residues of side chain A to regulate cross-linking of pectin in the cell wall. But the relationship of Api biosynthesis and RG-II dimer is still unclear. In this study we investigated the two homologous UDP-D-apiose/UDP-D-xylose synthases (AXSs) in Arabidopsis thaliana that synthesize UDP-D-apiose (UDP-Api). Both AXSs are ubiquitously expressed, while AXS2 has higher overall expression than AXS1 in the tissues analyzed. The homozygous axs double mutant is lethal, while heterozygous axs1/+ axs2 and axs1 axs2/+ mutants display intermediate phenotypes. The axs1/+ axs2 mutant plants are unable to set seed and die. By contrast, the axs1 axs2/+ mutant plants exhibit loss of shoot and root apical dominance. UDP-Api content in axs1 axs2/+ mutants is decreased by 83%. The cell wall of axs1 axs2/+ mutant plants is thicker and contains less RG-II-borate complex than wild-type Col-0 plants. Taken together, these results provide direct evidence of the importance of AXSs for UDP-Api and RG-II-borate complex formation in plant growth and development.

Genome-Wide Identification and Characterization of Short-Chain Dehydrogenase/Reductase (SDR) Gene Family in Medicago truncatula

“…MtSDR67E5 was highly expressed in all test tissues. MtSDR67E5 is homologous to UDP-D-apiose/UDP-D-xylose synthases (AXS2) confers synthesis of Rhamnogalacturonan-II (RG-II), which is one of major pectin types in M. truncatula [30]. SDR proteins were involved in many processes of primary and secondary metabolism [31].…”

Genome mapping and gene expression of NDP-sugar pathways in the giant duckweed Spirodela polyrhiza and its relevance for bioenergy

“…Xylan contributes to recalcitrance reduction by the polysaccharide length and arrangement with other cell wall polymers, consequently improving biofuel production [120]. On the other hand, apiose is essential for plant development [121,122]. In duckweeds, apiose is positively related to fast growth and negatively for starch accumulation [42].…”

<i>CsKDO</i> is a candidate gene regulating seed germination lethality in cucumber

“…The results obtained in the present study showed that cucumber CsKDO was a nuclear localization, which is different from its homologous from other crops including Arabidopsis AT1G53000 gene, indicating that functions between CsKDO and its homologous might be different, which might be caused by their localization differences. RG-II is a pectin molecule that is present in the primary cell wall of plants, it exist in the form of dimer, which is cross-linked by the borate diester bond between two arachidonic residues, containing 12 different glycosyl residues including aceric acid, apiose, 3-deoxy-D-lyxo-hept-2ulosaric acid 3-deoxy-D-manno-oct-2-ulosonic acid (KDO) and so on (Bar-Peled et al 2012, Kobayashi et al 1996, O'Neill et al 1996, 2004, Zhao et al 2020. The synthesis of dimer promotes the formation of pectin network, which promotes the mechanical properties of the primary wall and is necessary for the normal growth and development of plants, the absence of this dimer will lead to abnormal biochemical and biomechanical properties of the cell wall, even affect the productivity of plants (Julien et al 2018).…”