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Nitrate regulates floral induction in Arabidopsis, acting independently of light, gibberellin and autonomous pathways.

ABSTRACT: The transition from vegetative growth to reproduction is a major developmental event in plants. To maximise reproductive success, its timing is determined by complex interactions between environmental cues like the photoperiod, temperature and nutrient availability and internal genetic programs. While the photoperiod- and temperature- and gibberellic acid-signalling pathways have been subjected to extensive analysis, little is known about how nutrients regulate floral induction. This is partly because nutrient supply also has large effects on vegetative growth, making it difficult to distinguish primary and secondary influences on flowering. A growth system using glutamine supplementation was established to allow nitrate to be varied without a large effect on amino acid and protein levels, or the rate of growth. Under nitrate-limiting conditions, flowering was more rapid in neutral (12/12) or short (8/16) day conditions in C24, Col-0 and Laer. Low nitrate still accelerated flowering in late-flowering mutants impaired in the photoperiod, temperature, gibberellic acid and autonomous flowering pathways, in the fca co-2 ga1-3 triple mutant and in the ft-7 soc1-1 double mutant, showing that nitrate acts downstream of other known floral induction pathways. Several other abiotic stresses did not trigger flowering in fca co-2 ga1-3, suggesting that nitrate is not acting via general stress pathways. Low nitrate did not further accelerate flowering in long days (16/8) or in 35S::CO lines, and did override the late-flowering phenotype of 35S::FLC lines. We conclude that low nitrate induces flowering via a novel signalling pathway that acts downstream of, but interacts with, the known floral induction pathways.

SUBMITTER: Castro Marin I

PROVIDER: S-EPMC3043248 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Nitrate regulates floral induction in Arabidopsis, acting independently of light, gibberellin and autonomous pathways.

Castro Marín Inmaculada I Loef Irene I Bartetzko Linda L Searle Iain I Coupland George G Stitt Mark M Osuna Daniel D

Planta 20101127 3

The transition from vegetative growth to reproduction is a major developmental event in plants. To maximise reproductive success, its timing is determined by complex interactions between environmental cues like the photoperiod, temperature and nutrient availability and internal genetic programs. While the photoperiod- and temperature- and gibberellic acid-signalling pathways have been subjected to extensive analysis, little is known about how nutrients regulate floral induction. This is partly b ...[more]

PMID: 21113723

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Project description:The morphological variability of the flower in angiosperms, combined with its relatively simple structure, makes it an excellent model to study cell specification and the establishment of morphogenetic patterns. Flowers are the products of floral meristems, which are determinate structures that generate four different types of floral organs before terminating. The precise organization of the flower in whorls, each defined by the identity and number of organs it contains, is controlled by a multi-layered network involving numerous transcriptional regulators. In particular, the AGAMOUS (AG) MADS domain-containing transcription factor plays a major role in controlling floral determinacy in Arabidopsis thaliana in addition to specifying reproductive organ identity. This study aims to characterize the genetic interactions between the ULTRAPETALA1 (ULT1) and LEAFY (LFY) transcriptional regulators during flower morphogenesis, with a focus on AG regulation.Genetic and molecular approaches were used to address the question of redundancy and reciprocal interdependency for the establishment of flower meristem initiation, identity and termination. In particular, the effects of loss of both ULT1 and LFY function were determined by analysing flower developmental phenotypes of double-mutant plants. The dependency of each factor on the other for activating developmental genes was also investigated in gain-of-function experiments.The ULT1 and LFY pathways, while both activating AG expression in the centre of the flower meristem, functioned independently in floral meristem determinacy. Ectopic transcriptional activation by ULT1 of AG and AP3, another gene encoding a MADS domain-containing flower architect, did not depend on LFY function. Similarly, LFY did not require ULT1 function to ectopically determine floral fate.The results indicate that the ULT1 and LFY pathways act separately in regulating identity and determinacy at the floral meristem. In particular, they independently induce AG expression in the centre of the flower to terminate meristem activity. A model is proposed whereby these independent contributions bring about a switch at the AG locus from an inactive to an active transcriptional state at the correct time and place during flower development.

Dataset Information

Nitrate regulates floral induction in Arabidopsis, acting independently of light, gibberellin and autonomous pathways.

Publications

Nitrate regulates floral induction in Arabidopsis, acting independently of light, gibberellin and autonomous pathways.

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