Limits...
Interactions of CUP-SHAPED COTYLEDON and SPATULA genes control carpel margin development in Arabidopsis thaliana.

Nahar MA, Ishida T, Smyth DR, Tasaka M, Aida M - Plant Cell Physiol. (2012)

Bottom Line: In spt, transcripts of both CUC genes accumulated ectopically, and addition of cuc1 and cuc2 mutations to spt suppressed the split phenotype of carpels specifically along their lateral margins.In the basal gynoecium, on the other hand, all three genes promoted the formation of margin-derived structures, as revealed by the synergistic interactions of spt with each of the cuc mutations.Our results suggest that differential interactions among SPT, CUC1 and CUC2 direct the formation of domain-specific structures of the Arabidopsis gynoecium.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192 Japan.

ABSTRACT
A characteristic feature of flowering plants is the fusion of carpels, which results in the formation of an enclosed gynoecium. In Arabidopsis thaliana, the gynoecium is formed by the fusion of two carpels along their margins, which also act as a meristematic site for the formation of internal structures such as ovules, the septum and transmitting tract. How gene interactions coordinate the fusion and differentiation of the marginal structures during gynoecium development is largely unknown. It was previously shown that the SPATULA (SPT) gene is required for carpel fusion, whereas overexpression of the CUP-SHAPED COTYLEDON genes CUC1 and CUC2 prevents it. Here we provide evidence that SPT promotes carpel fusion in the apical gynoecium partly through the negative regulation of CUC1 and CUC2 expression. In spt, transcripts of both CUC genes accumulated ectopically, and addition of cuc1 and cuc2 mutations to spt suppressed the split phenotype of carpels specifically along their lateral margins. In the basal gynoecium, on the other hand, all three genes promoted the formation of margin-derived structures, as revealed by the synergistic interactions of spt with each of the cuc mutations. Our results suggest that differential interactions among SPT, CUC1 and CUC2 direct the formation of domain-specific structures of the Arabidopsis gynoecium.

Show MeSH
Early gynoecium development in wild-type, spt, cuc1 spt and cuc2 spt. (A–D) Stage 8 gynoecia viewed from above. (E–H) Lateral view of stage 11 gynoecia. (A) In the wild type, upward growth of the medial positions is more advanced than laterally, and ingrowths of the medial ridges meet at the center of the apical gynoecial tube. The inset diagram shows medial (m) and lateral (l) domains of the gynoecial tube. (B) In spt, a part of the medial region shows retarded apical growth (arrow). (C and D) In cuc1 spt (C) and cuc2 spt (D), apical growth of the gynoecial tube occurs evenly, but the inner medial surfaces fail to make contact due to reduced growth of the medial ridges. (E) In the wild type, the gynoecium closes at the upper end and begins to produce stigmatic papillae (arrow). (F) In spt, a central cleft deepens in the medial region (arrow). (G and H) In cuc1 spt (G) and cuc2 spt (H), the gynoecium continues to grow without any cleft. Bar in A, B, C, D = 50 µm; E–H = 150 µm. wt, wild type.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3367164&req=5

pcs057-F2: Early gynoecium development in wild-type, spt, cuc1 spt and cuc2 spt. (A–D) Stage 8 gynoecia viewed from above. (E–H) Lateral view of stage 11 gynoecia. (A) In the wild type, upward growth of the medial positions is more advanced than laterally, and ingrowths of the medial ridges meet at the center of the apical gynoecial tube. The inset diagram shows medial (m) and lateral (l) domains of the gynoecial tube. (B) In spt, a part of the medial region shows retarded apical growth (arrow). (C and D) In cuc1 spt (C) and cuc2 spt (D), apical growth of the gynoecial tube occurs evenly, but the inner medial surfaces fail to make contact due to reduced growth of the medial ridges. (E) In the wild type, the gynoecium closes at the upper end and begins to produce stigmatic papillae (arrow). (F) In spt, a central cleft deepens in the medial region (arrow). (G and H) In cuc1 spt (G) and cuc2 spt (H), the gynoecium continues to grow without any cleft. Bar in A, B, C, D = 50 µm; E–H = 150 µm. wt, wild type.

Mentions: In the wild-type gynoecial primordium, the upward growth in the medial region initially dominated that in the lateral region (stage 8; Fig. 2A) and then became even (stage 11; Fig. 2E), yielding a flat rim of apical tissues. The adaxial wall of the gynoecial cylinder initiates the medial ridges, which grew inward and fused post-genitally (Fig. 2A), resulting in the solid style (Fig. 1E). In the strong allele spt-2 (hereafter called spt), in contrast, the medial regions of the gynoecial rim showed retarded growth in the apical direction (arrow in Fig. 2B; Alvarez and Smyth 2002) and subsequently formed a cleft (arrow in Fig. 2F), manifesting the congenital fusion defect. In addition, the inward growth of the medial ridges decreased and failed to fill up the central hollow of the spt style (Figs. 1F, 2B). These results indicate that SPT promotes the growth of the apical medial domain in two ways: upward growth in the rim facilitates congenital carpel fusion and inward growth of the medial ridges fills up the central cavity.Fig. 2


Interactions of CUP-SHAPED COTYLEDON and SPATULA genes control carpel margin development in Arabidopsis thaliana.

Nahar MA, Ishida T, Smyth DR, Tasaka M, Aida M - Plant Cell Physiol. (2012)

Early gynoecium development in wild-type, spt, cuc1 spt and cuc2 spt. (A–D) Stage 8 gynoecia viewed from above. (E–H) Lateral view of stage 11 gynoecia. (A) In the wild type, upward growth of the medial positions is more advanced than laterally, and ingrowths of the medial ridges meet at the center of the apical gynoecial tube. The inset diagram shows medial (m) and lateral (l) domains of the gynoecial tube. (B) In spt, a part of the medial region shows retarded apical growth (arrow). (C and D) In cuc1 spt (C) and cuc2 spt (D), apical growth of the gynoecial tube occurs evenly, but the inner medial surfaces fail to make contact due to reduced growth of the medial ridges. (E) In the wild type, the gynoecium closes at the upper end and begins to produce stigmatic papillae (arrow). (F) In spt, a central cleft deepens in the medial region (arrow). (G and H) In cuc1 spt (G) and cuc2 spt (H), the gynoecium continues to grow without any cleft. Bar in A, B, C, D = 50 µm; E–H = 150 µm. wt, wild type.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3367164&req=5

pcs057-F2: Early gynoecium development in wild-type, spt, cuc1 spt and cuc2 spt. (A–D) Stage 8 gynoecia viewed from above. (E–H) Lateral view of stage 11 gynoecia. (A) In the wild type, upward growth of the medial positions is more advanced than laterally, and ingrowths of the medial ridges meet at the center of the apical gynoecial tube. The inset diagram shows medial (m) and lateral (l) domains of the gynoecial tube. (B) In spt, a part of the medial region shows retarded apical growth (arrow). (C and D) In cuc1 spt (C) and cuc2 spt (D), apical growth of the gynoecial tube occurs evenly, but the inner medial surfaces fail to make contact due to reduced growth of the medial ridges. (E) In the wild type, the gynoecium closes at the upper end and begins to produce stigmatic papillae (arrow). (F) In spt, a central cleft deepens in the medial region (arrow). (G and H) In cuc1 spt (G) and cuc2 spt (H), the gynoecium continues to grow without any cleft. Bar in A, B, C, D = 50 µm; E–H = 150 µm. wt, wild type.
Mentions: In the wild-type gynoecial primordium, the upward growth in the medial region initially dominated that in the lateral region (stage 8; Fig. 2A) and then became even (stage 11; Fig. 2E), yielding a flat rim of apical tissues. The adaxial wall of the gynoecial cylinder initiates the medial ridges, which grew inward and fused post-genitally (Fig. 2A), resulting in the solid style (Fig. 1E). In the strong allele spt-2 (hereafter called spt), in contrast, the medial regions of the gynoecial rim showed retarded growth in the apical direction (arrow in Fig. 2B; Alvarez and Smyth 2002) and subsequently formed a cleft (arrow in Fig. 2F), manifesting the congenital fusion defect. In addition, the inward growth of the medial ridges decreased and failed to fill up the central hollow of the spt style (Figs. 1F, 2B). These results indicate that SPT promotes the growth of the apical medial domain in two ways: upward growth in the rim facilitates congenital carpel fusion and inward growth of the medial ridges fills up the central cavity.Fig. 2

Bottom Line: In spt, transcripts of both CUC genes accumulated ectopically, and addition of cuc1 and cuc2 mutations to spt suppressed the split phenotype of carpels specifically along their lateral margins.In the basal gynoecium, on the other hand, all three genes promoted the formation of margin-derived structures, as revealed by the synergistic interactions of spt with each of the cuc mutations.Our results suggest that differential interactions among SPT, CUC1 and CUC2 direct the formation of domain-specific structures of the Arabidopsis gynoecium.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara, 630-0192 Japan.

ABSTRACT
A characteristic feature of flowering plants is the fusion of carpels, which results in the formation of an enclosed gynoecium. In Arabidopsis thaliana, the gynoecium is formed by the fusion of two carpels along their margins, which also act as a meristematic site for the formation of internal structures such as ovules, the septum and transmitting tract. How gene interactions coordinate the fusion and differentiation of the marginal structures during gynoecium development is largely unknown. It was previously shown that the SPATULA (SPT) gene is required for carpel fusion, whereas overexpression of the CUP-SHAPED COTYLEDON genes CUC1 and CUC2 prevents it. Here we provide evidence that SPT promotes carpel fusion in the apical gynoecium partly through the negative regulation of CUC1 and CUC2 expression. In spt, transcripts of both CUC genes accumulated ectopically, and addition of cuc1 and cuc2 mutations to spt suppressed the split phenotype of carpels specifically along their lateral margins. In the basal gynoecium, on the other hand, all three genes promoted the formation of margin-derived structures, as revealed by the synergistic interactions of spt with each of the cuc mutations. Our results suggest that differential interactions among SPT, CUC1 and CUC2 direct the formation of domain-specific structures of the Arabidopsis gynoecium.

Show MeSH