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CLE19 expressed in the embryo regulates both cotyledon establishment and endosperm development in Arabidopsis.

Xu TT, Ren SC, Song XF, Liu CM - J. Exp. Bot. (2015)

Bottom Line: CLE19 is expressed in the epidermal layers of the cotyledon primordia, hypocotyl, and root cap in the embryo.Transgenic plants carrying an antagonistic CLE19 G6T construct expressed under the control of CLE19 regulatory elements exhibited a dominant seed abortion phenotype, with defective cotyledon establishment in embryos and delayed nuclear proliferation and cellularization in endosperms.We therefore propose that CLE19 may act as a mobile peptide co-ordinating embryo and endosperm development.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China University of Chinese Academy of Sciences, Beijing 100049, China.

No MeSH data available.


Related in: MedlinePlus

Defective embryo and endosperm development in pCLE19:CLE19G6T:tCLE19 transgenic plants. (A) Siliques from wild-type (WT) and pCLE19:CLE19G6T:tCLE19 transgenic plants (CLE19G6T), showing aborted ovules (indicated by arrowheads) at 12 DAP. (B–I) DIC microscopic observations of cleared ovules from wild-type (B, C, F, G) and pCLE19:CLE19G6T:tCLE19 transgenic plants (D, E, H, I) at 5 (B–E), 7 (F, H), and 12 DAP (G, I). Note the reduced sizes of embryo sacs in (D), and decreased numbers of endosperm nuclei in (E), as compared with (B) and (C), while there is no obvious defect in the embryo (indicated by arrowheads) at this stage. Delayed cotyledon formation (indicated by arrowheads) in embryos from pCLE19:CLE19G6T:tCLE19 transgenic plants at 7 (H) and 12 DAP (I), as compared with wild-type ovules at the same stages (F, G). (J–M) Cytohistological analyses of embryos and endosperms in the wild-type (J, L) and pCLE19:CLE19G6T:tCLE19 transgenic plants (K, M) at 5 (J, K) and 12 DAP (L, M), to show the delayed endosperm cellularization (indicated by asterisks) and defective cotyledon establishment (indicated by arrowheads) in ovules from pCLE19:CLE19G6T:tCLE19 transgenic plants (K, M), as compared with the wild type at the corresponding stages (J, L). c, cotyledon; h, hypocotyl; e, endosperm. Scale bars: in A=500 μm; in B–E=100 μm; in F and H=50 μm; in G and I=100 μm; and in J–M=50 μm.
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Figure 1: Defective embryo and endosperm development in pCLE19:CLE19G6T:tCLE19 transgenic plants. (A) Siliques from wild-type (WT) and pCLE19:CLE19G6T:tCLE19 transgenic plants (CLE19G6T), showing aborted ovules (indicated by arrowheads) at 12 DAP. (B–I) DIC microscopic observations of cleared ovules from wild-type (B, C, F, G) and pCLE19:CLE19G6T:tCLE19 transgenic plants (D, E, H, I) at 5 (B–E), 7 (F, H), and 12 DAP (G, I). Note the reduced sizes of embryo sacs in (D), and decreased numbers of endosperm nuclei in (E), as compared with (B) and (C), while there is no obvious defect in the embryo (indicated by arrowheads) at this stage. Delayed cotyledon formation (indicated by arrowheads) in embryos from pCLE19:CLE19G6T:tCLE19 transgenic plants at 7 (H) and 12 DAP (I), as compared with wild-type ovules at the same stages (F, G). (J–M) Cytohistological analyses of embryos and endosperms in the wild-type (J, L) and pCLE19:CLE19G6T:tCLE19 transgenic plants (K, M) at 5 (J, K) and 12 DAP (L, M), to show the delayed endosperm cellularization (indicated by asterisks) and defective cotyledon establishment (indicated by arrowheads) in ovules from pCLE19:CLE19G6T:tCLE19 transgenic plants (K, M), as compared with the wild type at the corresponding stages (J, L). c, cotyledon; h, hypocotyl; e, endosperm. Scale bars: in A=500 μm; in B–E=100 μm; in F and H=50 μm; in G and I=100 μm; and in J–M=50 μm.

Mentions: It has been shown previously that BnCLE19 is an embryo-specific gene expressed in cotyledon primordia in triangular-stage embryos, and in the epidermal layer of cotyledons in heart-shape and torpedo-stage embryos (Fiers et al., 2004). In this study, the antagonistic pCLE19:CLE19G6T:tCLE19 construct (Song et al., 2013) was devised to elucidate the role of CLE19 in Arabidopsis. The construct consisted of a 1782bp 5′ upstream region (pCLE19), a 225bp coding region, and a 1205bp 3′ downstream sequence (tCLE19) of CLE19, with the conserved sixth glycine in the CLE motif substituted by threonine. The construct was transformed into Arabidopsis (Col-0) using the floral dip method (Clough and Bent, 1998). Among 54 independent T1 transgenic lines examined, 12 showed different percentages of seed abortions, and among these 12 lines, three (#1, #2, and #3) exhibited consistently high frequencies of a seed abortion phenotype (Fig. 1A). Examination of seeds at 12 days after pollination (DAP) under a dissection microscope revealed that 36.3, 33.8, and 33.4% of ovules in lines #1, #2, and #3, respectively, were aborted before maturation (Table 1). Progeny plants produced from these three lines showed a consistent seed abortion phenotype for four generations examined so far. The transgenic plants were pollinated with pollen from wild-type plants, and the resultant ovules showed similar frequencies of seed abortion, indicating that the abortion phenotype was a dominant trait. The phenotypes of these three transgenic lines were indistinguishable from one another, and transgenic line #1 was used in all subsequent studies.


CLE19 expressed in the embryo regulates both cotyledon establishment and endosperm development in Arabidopsis.

Xu TT, Ren SC, Song XF, Liu CM - J. Exp. Bot. (2015)

Defective embryo and endosperm development in pCLE19:CLE19G6T:tCLE19 transgenic plants. (A) Siliques from wild-type (WT) and pCLE19:CLE19G6T:tCLE19 transgenic plants (CLE19G6T), showing aborted ovules (indicated by arrowheads) at 12 DAP. (B–I) DIC microscopic observations of cleared ovules from wild-type (B, C, F, G) and pCLE19:CLE19G6T:tCLE19 transgenic plants (D, E, H, I) at 5 (B–E), 7 (F, H), and 12 DAP (G, I). Note the reduced sizes of embryo sacs in (D), and decreased numbers of endosperm nuclei in (E), as compared with (B) and (C), while there is no obvious defect in the embryo (indicated by arrowheads) at this stage. Delayed cotyledon formation (indicated by arrowheads) in embryos from pCLE19:CLE19G6T:tCLE19 transgenic plants at 7 (H) and 12 DAP (I), as compared with wild-type ovules at the same stages (F, G). (J–M) Cytohistological analyses of embryos and endosperms in the wild-type (J, L) and pCLE19:CLE19G6T:tCLE19 transgenic plants (K, M) at 5 (J, K) and 12 DAP (L, M), to show the delayed endosperm cellularization (indicated by asterisks) and defective cotyledon establishment (indicated by arrowheads) in ovules from pCLE19:CLE19G6T:tCLE19 transgenic plants (K, M), as compared with the wild type at the corresponding stages (J, L). c, cotyledon; h, hypocotyl; e, endosperm. Scale bars: in A=500 μm; in B–E=100 μm; in F and H=50 μm; in G and I=100 μm; and in J–M=50 μm.
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Figure 1: Defective embryo and endosperm development in pCLE19:CLE19G6T:tCLE19 transgenic plants. (A) Siliques from wild-type (WT) and pCLE19:CLE19G6T:tCLE19 transgenic plants (CLE19G6T), showing aborted ovules (indicated by arrowheads) at 12 DAP. (B–I) DIC microscopic observations of cleared ovules from wild-type (B, C, F, G) and pCLE19:CLE19G6T:tCLE19 transgenic plants (D, E, H, I) at 5 (B–E), 7 (F, H), and 12 DAP (G, I). Note the reduced sizes of embryo sacs in (D), and decreased numbers of endosperm nuclei in (E), as compared with (B) and (C), while there is no obvious defect in the embryo (indicated by arrowheads) at this stage. Delayed cotyledon formation (indicated by arrowheads) in embryos from pCLE19:CLE19G6T:tCLE19 transgenic plants at 7 (H) and 12 DAP (I), as compared with wild-type ovules at the same stages (F, G). (J–M) Cytohistological analyses of embryos and endosperms in the wild-type (J, L) and pCLE19:CLE19G6T:tCLE19 transgenic plants (K, M) at 5 (J, K) and 12 DAP (L, M), to show the delayed endosperm cellularization (indicated by asterisks) and defective cotyledon establishment (indicated by arrowheads) in ovules from pCLE19:CLE19G6T:tCLE19 transgenic plants (K, M), as compared with the wild type at the corresponding stages (J, L). c, cotyledon; h, hypocotyl; e, endosperm. Scale bars: in A=500 μm; in B–E=100 μm; in F and H=50 μm; in G and I=100 μm; and in J–M=50 μm.
Mentions: It has been shown previously that BnCLE19 is an embryo-specific gene expressed in cotyledon primordia in triangular-stage embryos, and in the epidermal layer of cotyledons in heart-shape and torpedo-stage embryos (Fiers et al., 2004). In this study, the antagonistic pCLE19:CLE19G6T:tCLE19 construct (Song et al., 2013) was devised to elucidate the role of CLE19 in Arabidopsis. The construct consisted of a 1782bp 5′ upstream region (pCLE19), a 225bp coding region, and a 1205bp 3′ downstream sequence (tCLE19) of CLE19, with the conserved sixth glycine in the CLE motif substituted by threonine. The construct was transformed into Arabidopsis (Col-0) using the floral dip method (Clough and Bent, 1998). Among 54 independent T1 transgenic lines examined, 12 showed different percentages of seed abortions, and among these 12 lines, three (#1, #2, and #3) exhibited consistently high frequencies of a seed abortion phenotype (Fig. 1A). Examination of seeds at 12 days after pollination (DAP) under a dissection microscope revealed that 36.3, 33.8, and 33.4% of ovules in lines #1, #2, and #3, respectively, were aborted before maturation (Table 1). Progeny plants produced from these three lines showed a consistent seed abortion phenotype for four generations examined so far. The transgenic plants were pollinated with pollen from wild-type plants, and the resultant ovules showed similar frequencies of seed abortion, indicating that the abortion phenotype was a dominant trait. The phenotypes of these three transgenic lines were indistinguishable from one another, and transgenic line #1 was used in all subsequent studies.

Bottom Line: CLE19 is expressed in the epidermal layers of the cotyledon primordia, hypocotyl, and root cap in the embryo.Transgenic plants carrying an antagonistic CLE19 G6T construct expressed under the control of CLE19 regulatory elements exhibited a dominant seed abortion phenotype, with defective cotyledon establishment in embryos and delayed nuclear proliferation and cellularization in endosperms.We therefore propose that CLE19 may act as a mobile peptide co-ordinating embryo and endosperm development.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Fragrant Hill, Beijing 100093, China University of Chinese Academy of Sciences, Beijing 100049, China.

No MeSH data available.


Related in: MedlinePlus