HEN1 functions pleiotropically in Arabidopsis development and acts in C function in the flower - PubMed (original) (raw)

HEN1 functions pleiotropically in Arabidopsis development and acts in C function in the flower

Xuemei Chen et al. Development. 2002 Mar.

Abstract

Four classes of floral homeotic MADS domain proteins specify the identities of the four organ types in an Arabidopsis flower. While the activities of the MADS domain proteins are essentially confined to the flower or to the inflorescence, several genes, such as APETALA2, HUA1 and HUA2, also act outside the flower in addition to their organ identity functions inside the flower. We identified a new gene, HUA ENHANCER 1 (HEN1) from a sensitized genetic screen in the hua1-1 hua2-1 background that is compromised in floral homeotic C function. We showed that HEN1, like the C function gene AGAMOUS, acts to specify reproductive organ identities and to repress A function. HEN1 also shares AG's non-homeotic function in controlling floral determinacy. HEN1 may achieve these functions by regulating the expression of AG. hen1 single mutants exhibit pleiotropic phenotypes such as reduced organ size, altered rosette leaf shape and increased number of coflorescences, during most stages of development. Therefore, HEN1, like the A function gene AP2, plays multiple roles in plant development as well as acting in organ identity specification in the flower. HEN1 codes for a novel protein and is expressed throughout the plant.

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Figures

Fig. 1

Fig. 1

hen1-1 and hen1-2 single mutant phenotypes. (A–C) Rosettes of (A) a L_er_, (B) a hen1-1 and (C) a hen1-2 plant, around the time of bolting. Rosette leaves in hen1-1 and hen1-2 tend to be pointed (arrows), and the edges tend to curl up slightly (arrowhead). (D) A hen1-1 plant containing the HEN1p10/p11 transgene. (E) A L_er_ (left) and a hen1-1 (right) mature flower at the same magnification. (F) A L_er_ and (G) a hen1-1 inflorescence. (H–J) Scanning electron micrographs of (H) a L_er_, (I) a hen1-1 and (J) a hen1-2 mature leaf. (K–M) Scanning electron micrographs of (K) a L_er_, (L) a hen1-1 and (M) a hen1-2 mature petal. Scale bars, 100 µm in H–J, and 10 µm in K–M.

Fig. 2

Fig. 2

Floral phenotypes. (A) A hua1-1 hua2-1, (B) a hua1-1 hua2-1 hen1-1, and (C) a hua1-1 hua2-1 hen1-2 flower. (D) A late-arising hua1-1 hua2-1 hen1-2 flower. The gynoecium is enlarged with a gynophore at the base (arrowhead). (E) A late-arising hua1-1 hua2-1 hen1-2 flower with additional floral organs (arrowhead) inside the carpels. (F) A late-arising hua1-1 hua2-1 hen1-1 flower with flowers (arrowhead) in place of carpels. (G) A hua1-1 hen1-1 and (H) a hua2-1 hen1-1 flower. (I) A flower of a hua1-1 hua2-1 hen1-1 plant containing the HEN1p10/p11 transgene. Arrows, third whorl organs. Scale bars, 1 mm.

Fig. 3

Fig. 3

Scanning electron microscope images of L_er_, hen1-1, hua1-1 hua2-1, hua1-1 hua2-1 hen1-1 and hua1-1 hua2-1 hen1-2 flowers and/or floral organs. (A–C) The adaxial surface of the third whorl organs from (A) hua1-1 hua2-1, (B) hua1-1 hua2-1 hen1-1 and (C) hua1-1 hua2-1 hen1-2 flowers. Petal-type cells are found in the third whorl organs in the two triple mutants (B,C). (D) The top portion of a L_er_ ovary, showing valve cells that lack cuticular thickenings. (E,F) The tip (E) and the bottom (F) of a hua1-1 hua2-1 ovary. Some valve cells at the tip of the ovary exhibit cuticular striations that mimic sepal cells (E). The bottom of the hua1-1 hua2-1 ovary is similar to that in L_er_ in terms of cell surface characteristics. (G,H) The bottom portion of ovaries from (G) a hua1-1 hua2-1 hen1-1 and (H) a hua1-1 hua2-1 hen1-2 flower. The cells resemble sepal cells. (I,J) Top portions of the ovaries from (I) a hua1-1 hen1-1 and (J) a hua2-1 hen1-1 flower. The cells appear wild type. (K,L) Stage 7–8 flowers of (K) hua1-1 hua2-1 and (L) hua1-1 hua2-1 hen1-1 genotypes, with sepals dissected to reveal the third whorl organs (arrows) that differ in shapes. Scale bars, 10 µm except in K and L (100 µm).

Fig. 4

Fig. 4

AP1 and AG RNA accumulation patterns in hua1-1 hua2-1 and hua1-1 hua2-1 hen1-1 flowers. (A–H) AP1 RNA localization in hua1-1 hua2-1 (A–D) and hua1-1 hua2-1 hen1-1 (E–H) flowers of various stages. (A,E) Stage 3 flowers; (B,F) stage 6–7 flowers; (C,G) stages 9–10 flowers. (D,H) Mature flowers. Arrows indicate ectopic AP1 expression. In hua1-1 hua2-1 hen1-1 flowers, the ectopic AP1 expression is more precocious (arrows in E and F) and extensive (G and H). (I–L) AG RNA localization in (I,K) hua1-1 hua2-1 and (J,L) hua1-1 hua2-1 hen1-1 flowers. (I,J) AG expression in young flowers (stages indicated by numbers). (K,L) Stage 9 flowers. The arrow in L indicates a fourth whorl organ with little AG RNA. Se, sepals; St, stamens; C, carpels. Numbers in G and L indicate floral whorls. Scale bars, 50 µm.

Fig. 5

Fig. 5

Third whorl identity and A function genes. (A) a hua1-1 hua2-1 hen1-1 flower, (C) a hua1-1 hua2-1 hen1-1 ap1-1 flower and (E) a hua1-1 hua2-1 hen1-1 ap2-2 flower. (B,D,F) Dissected third whorl organs from the flowers in A, C and E, respectively. Scale bars: 1 mm.

Fig. 6

Fig. 6

Cloning of HEN1. (A) Mapping of HEN1 to the BAC T13K14 on chromosome IV. The HEN1 genomic region is represented by the long horizontal line. The markers used for mapping are shown above the line with the numbers of recombination break points between HEN1 and those markers shown. (B) The HEN1 protein sequence from L_er_. HEN1 codes for a novel protein with a C-terminal domain (underlined) showing similarity to yeast, C. elegans and Drosophila proteins. The hen1-1 and hen1-2 mutations cause truncation and amino acid substitution, respectively, in the C-terminal domain. A potential nuclear localization signal (NLS) is boxed. The amino acids from Col and WS that differ from those in L_er_ are indicated above the sequence.

Fig. 7

Fig. 7

HEN1 RNA accumulation. HEN1 RNA can be detected in roots (R), stems (S), leaves (L) and inflorescences (In). UBQ5 was used as a loading control. The relative abundance of HEN1 RNA in these tissues was calculated based on quantification with a phosphorimager.

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