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Summary Accumulation of triacylglycerols (TAGs) is crucial during various stages of plant development. InArabidopsis, two enzymes share overlapping functions to produce TAGs, namely acyl‐CoA:diacylglycerol acyltransferase 1 (DGAT1) and phospholipid:diacylglycerol acyltransferase 1 (PDAT1). Loss of function of both genes in adgat1‐1/pdat1‐2double mutant is gametophyte lethal. However, the key regulatory elements controlling tissue‐specific expression of either gene has not yet been identified.We transformed adgat1‐1/dgat1‐1//PDAT1/pdat1‐2parent with transgenic constructs containing theArabidopsis DGAT1promoter fused to theAtDGAT1open reading frame either with or without the first intron.Triple homozygous plants were obtained, however, in the absence of theDGAT1first intron anthers fail to fill with pollen, seed yield isc. 10% of wild‐type, seed oil content remains reduced (similar todgat1‐1/dgat1‐1), and non‐Mendelian segregation of thePDAT1/pdat1‐2locus occurs. Whereas plants expressing theAtDGAT1pro:AtDGAT1transgene containing the first intron mostly recover phenotypes to wild‐type.This study establishes that a combination of the promoter and first intron ofAtDGAT1provides the proper context for temporal and tissue‐specific expression ofAtDGAT1in pollen. Furthermore, we discuss possible mechanisms of intron mediated regulation and how regulatory elements can be used as genetic tools to functionally replace TAG biosynthetic enzymes inArabidopsis.
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The Arabidopsis xylosyltransferases, XXT3 , XXT4 , and XXT5, are essential to complete the fully xylosylated glucan backbone XXXG ‐type structure of xyloglucans
Summary Although most xyloglucans (XyGs) biosynthesis enzymes have been identified, the molecular mechanism that defines XyG branching patterns is unclear. Four out of five XyG xylosyltransferases (XXT1, XXT2, XXT4, and XXT5) are known to add the xylosyl residue from UDP‐xylose onto a glucan backbone chain; however, the function of XXT3 has yet to be demonstrated.Singlexxt3and triplexxt3xxt4xxt5mutantArabidopsis(Arabidopsis thaliana) plants were generated using CRISPR‐Cas9 technology to determine the specific function of XXT3.Combined biochemical, bioinformatic, and morphological data conclusively established for the first time that XXT3, together with XXT4 and XXT5, adds xylosyl residue specifically at the third glucose in the glucan chain to synthesize XXXG‐type XyGs. We propose that the specificity of XXT3, XXT4, and XXT5 is directed toward the prior synthesis of the acceptor substrate by the other two enzymes, XXT1 and XXT2. We also conclude that XXT5 plays a dominant role in the synthesis of XXXG‐type XyGs, while XXT3 and XXT4 complementarily contribute their activities in a tissue‐specific manner.The newly generatedxxt3xxt4xxt5mutant produces only XXGG‐type XyGs, which further helps to understand the impact of structurally deficient polysaccharides on plant cell wall organization, growth, and development.
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- PAR ID:
- 10405637
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- New Phytologist
- Volume:
- 238
- Issue:
- 5
- ISSN:
- 0028-646X
- Page Range / eLocation ID:
- p. 1986-1999
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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