Dataset Information

FILAMENTOUS FLOWER, a meristem and organ identity gene of Arabidopsis, encodes a protein with a zinc finger and HMG-related domains.

ABSTRACT: Distinctive from that of the animal system, the basic plan of the plant body is the continuous formation of a structural unit, composed of a stem with a meristem at the top and lateral organs continuously forming at the meristem. Therefore, mechanisms controlling the formation, maintenance, and development of a meristem will be a key to understanding the body plan of higher plants. Genetic analyses of filamentous flower (fil) mutants have indicated that FIL is required for the maintenance and growth of inflorescence and floral meristems, and of floral organs of Arabidopsis thaliana. FIL encodes a protein carrying a zinc finger and a HMG box-like domain, which is known to work as a transcription regulator. As expected, the FIL protein was shown to have a nuclear location. In situ hybridization clearly demonstrated that FIL is expressed only at the abaxial side of primordia of leaves and floral organs. Transgenic plants, ectopically expressing FIL, formed filament-like leaves with randomly arranged cells at the leaf margin. Our results indicate that cells at the abaxial side of the lateral organs are responsible for the normal development of the organs as well as for maintaining the activity of meristems.

SUBMITTER: Sawa S

PROVIDER: S-EPMC316944 | biostudies-literature | 1999 May

REPOSITORIES: biostudies-literature

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FILAMENTOUS FLOWER, a meristem and organ identity gene of Arabidopsis, encodes a protein with a zinc finger and HMG-related domains.

Sawa S S Watanabe K K Goto K K Liu Y G YG Shibata D D Kanaya E E Morita E H EH Okada K K

Genes & development 19990501 9

Distinctive from that of the animal system, the basic plan of the plant body is the continuous formation of a structural unit, composed of a stem with a meristem at the top and lateral organs continuously forming at the meristem. Therefore, mechanisms controlling the formation, maintenance, and development of a meristem will be a key to understanding the body plan of higher plants. Genetic analyses of filamentous flower (fil) mutants have indicated that FIL is required for the maintenance and gr ...[more]

PMID: 10323860

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Project description:BackgroundThe YABBY (YAB) family of transcription factors participate in a diverse range of processes that include leaf and floral patterning, organ growth, and the control of shoot apical meristem organisation and activity. How these disparate functions are regulated is not clear, but based on interactions with the LEUNIG-class of co-repressors, it has been proposed that YABs act as transcriptional repressors. In the light of recent work showing that DNA-binding proteins associated with the yeast co-repressor TUP1 can also function as activators, we have examined the transcriptional activity of the YABs.ResultsOf the four Arabidopsis YABs tested in yeast, only FILAMENTOUS FLOWER (FIL) activated reporter gene expression. Similar analysis with Antirrhinum YABs identified the FIL ortholog GRAMINIFOLIA as an activator. Plant-based transactivation assays not only confirmed the potential of FIL to activate transcription, but also extended this property to the FIL paralog YABBY3 (YAB3). Subsequent transcriptomic analysis of lines expressing a steroid-inducible FIL protein revealed groups of genes that responded either positively or negatively to YAB induction. Included in the positively regulated group of genes were the polarity regulators KANADI1 (KAN1), AUXIN RESPONSE FACTOR 4 (ARF4) and ASYMMETRIC LEAVES1 (AS1). We also show that modifying FIL to function as an obligate repressor causes strong yab loss-of-function phenotypes.ConclusionsCollectively these data show that FIL functions as a transcriptional activator in plants and that this activity is involved in leaf patterning. Interestingly, our study also supports the idea that FIL can act as a repressor, as transcriptomic analysis identified negatively regulated FIL-response genes. To reconcile these observations, we propose that YABs are bifunctional transcription factors that participate in both positive and negative regulation. These findings fit a model of leaf development in which adaxial/abaxial patterning is maintained by a regulatory network consisting of positive feedback loops.

Project description:BackgroundThe ornamental crop Calluna vulgaris is of increasing importance to the horticultural industry in the northern hemisphere due to a flower organ mutation: the flowers of the 'bud-flowering' phenotype remain closed i.e. as buds throughout the total flowering period and thereby maintain more colorful flowers for a longer period of time than the wild-type. This feature is accompanied and presumably caused by the complete lack of stamens. Descriptions of this botanical particularity are inconsistent and partially conflicting. In order to clarify basic questions of flower organ identity in general and stamen loss in detail, a study of the wild-type and the 'bud-flowering' flower type of C. vulgaris was initiated.ResultsFlowers were examined by macro- and microscopic techniques. Organ development was investigated comparatively in both the wild-type and the 'bud-flowering' type by histological analyses. Analysis of epidermal cell surface structure of vegetative tissues and perianth organs using scanning electron microscopy revealed that in wild-type flowers the outer whorls of colored organs may be identified as sepals, while the inner ones may be identified as petals. In the 'bud-flowering' type, two whorls of sepals are directly followed by the gynoecium. Both, petals and stamens, are completely missing in this flower type. The uppermost whorl of green leaves represents bracts in both flower types. In addition, two MADS-box genes (homologs of AP3/DEF and SEP1/2) were identified in C. vulgaris using RACE-PCR. Expression analysis by qRT-PCR was conducted for both genes in leaves, bracts, sepals and petals. These experiments revealed an expression pattern supporting the organ classification based on morphological characteristics.ConclusionsOrgan identity in both wild-type and 'bud-flowering' C. vulgaris was clarified using a combination of microscopic and molecular methods. Our results for bract, sepal and petal organ identity are supported by the 'ABCDE model'. However, loss of stamens in the 'bud-flowering' phenotype is an exceptional flower organ modification that cannot be explained by modified spatial expression of known organ identity genes.

Dataset Information

FILAMENTOUS FLOWER, a meristem and organ identity gene of Arabidopsis, encodes a protein with a zinc finger and HMG-related domains.

Publications

FILAMENTOUS FLOWER, a meristem and organ identity gene of Arabidopsis, encodes a protein with a zinc finger and HMG-related domains.

Similar Datasets

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