AtCSLA7, a cellulose synthase-like putative glycosyltransferase, is important for pollen tube growth and embryogenesis in Arabidopsis - PubMed (original) (raw)

AtCSLA7, a cellulose synthase-like putative glycosyltransferase, is important for pollen tube growth and embryogenesis in Arabidopsis

Florence Goubet et al. Plant Physiol. 2003 Feb.

Abstract

The cellulose synthase-like proteins are a large family of proteins in plants thought to be processive polysaccharide beta-glycosyltransferases. We have characterized an Arabidopsis mutant with a transposon insertion in the gene encoding AtCSLA7 of the CSLA subfamily. Analysis of the transmission efficiency of the insertion indicated that AtCSLA7 is important for pollen tube growth. Moreover, the homozygous insertion was embryo lethal. A detailed analysis of seed developmental progression revealed that mutant embryos developed more slowly than wild-type siblings. The mutant embryos also showed abnormal cell patterning and they arrested at a globular stage. The defective embryonic development was associated with reduced proliferation and failed cellularization of the endosperm. AtCSLA7 is widely expressed, and is likely to be required for synthesis of a cell wall polysaccharide found throughout the plant. Our results suggest that this polysaccharide is essential for cell wall structure or for signaling during plant embryo development.

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Figures

Figure 1

Figure 1

Structure of the predicted AtCSLA7 gene and AtCSLA7 protein. A, Position of introns, exons, and Ds insertion in AtCSLA7. Rectangular boxes represent the exons and the lines represent introns in the gene. Light-gray rectangles are untranslated regions. Start and stop codons are indicated. The dark-gray rectangle represents the Ds insertion. Numbers refer to nucleotide position in the BAC T20F21. B, AtCSLA7 protein. Underlined amino acids correspond to the putative transmembrane domains of the protein. Shaded characters are the amino acids conserved in most members of the CSLA family. Bold characters are highly conserved amino acids in CSL, CELA, and CESA families. Boxes represent the D,D,D,QXXRW motif characteristic of β-glycosyltransferases. C, Topology model of AtCSLA7.

Figure 2

Figure 2

The expression of AtCSLA7 in different plant tissues: analysis by RT-PCR using internal primers 1 and 4. 1 through 12, PCR products from RT-PCR reaction (approximately 1.5 kb); 13, PCR product from genomic amplification (approximately 2 kb). 1, Four-day-old callus; 2, 7-d-old callus; 3, 7-d-old plantlets; 4, roots; 5, leaves of rosettes; 6, young stems before flowering; 7, whole old stems including flowers, siliques, and leaves; 8, stems alone; 9, leaves of stem; 10, flowers; 11, pollen; 12, young siliques; 13, genomic DNA.

Figure 3

Figure 3

Seed and embryo morphology in hemizygous SGT4425 plants. A, Dissected silique at cotyledonary stage showing WT (green) and aborted (white) seeds. Aborted seeds (arrows) are unequally distributed within the silique, biased toward the apical half. B and C, Phenotype of a normal (B) and an aborted (C) seed from a cotyledonary stage silique. The mutant embryo is arrested at globular stage and peripheral free nuclear endosperm is still visible (arrowheads). Bars = 50 μm in B and C.

Figure 4

Figure 4

Embryo development in WT (A–D) and SGT4425 mutant (E–H) embryos present within siliques of hemizygous SGT4425 plants at different developmental stages. A and E, Sixteen-cell embryo proper stage; B and F, mid-globular stage; C and G, late globular transition stage; D and H, late heart stage of WT embryos. E, Abnormal eight-cell embryo proper with altered axial and transverse divisions. F, Abnormal early globular embryo. G and H, Abnormal embryos containing 28 to 46 cells showing abnormal transverse divisions and incomplete protoderm formation. Bars = 10 μm in A through C and E through H. Bar = 20 μm in D.

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