Model-assisted physiological analysis of Phyllo, a rice architectural mutant

Luquet Delphine, Song You Hong, Elbelt Sonia, This Dominique, Clément-Vidal Anne, Perin Christophe, Fabre Denis, Dingkuhn Michaël. 2007. Model-assisted physiological analysis of Phyllo, a rice architectural mutant. Functional Plant Biology, 34 (1) : 11-23.

Résumé : Studies of phenotype of knockout mutants can provide new insights into physiological, phenological and architectural feedbacks in the plant system. Phyllo, a mutant of Nippon Bare rice (Oryza sativa L.) producing small leaves in rapid succession, was isolated during multiplication of a T-DNA insertion library. Phyllo phenotype was compared with the wild type (WT) during vegetative development in hydroponics culture using a wide range of physiological and biometric measurements. These were integrated with the help of the functional-structural model EcoMeristem, explicitly designed to study interactions between morphogenesis and carbon assimilation. Although the phenotype of the mutant was caused by a single recessive gene, it differed in many ways from the WT, suggesting a pleiotropic effect of this mutation. Phyllochron was 25 (1-4 leaf stage) to 38% (>>4 leaf stage) shorter but showed normal transition from juvenile to adult phase after leaf 4. Leaf size also increased steadily with leaf position as in WT. The mutant had reduced leaf blade length: width and blade: sheath length ratios, particularly during the transition from heterotrophic to autotrophic growth. During the same period, root: shoot dry weight ratio was significantly diminished. Specific leaf area (SLA) was strongly increased in the mutant but showed normal descending patterns with leaf position. Probably related to high SLA, the mutant had much lower light-saturated leaf photosynthetic rates and lower radiation use efficiency (RUE) than the WT. Leaf extension rates were strongly reduced in absolute terms but were high in relative terms (normalised by final leaf length). The application of the EcoMeristem model to these data indicated that the mutant was severely deficient in assimilate, resulting from low RUE and high organ initiation rate causing high assimilate demand. This was particularly pronounced during the heterotrophic-autotrophic transition, probably causing shorter leaf blades relative to sheaths, as well as a temporary reduction of assimilate partitioning to roots. The model accurately simulated the mutant's high leaf mortality and absence of tillering. The simulated assimilate shortage was supported by observed reductions in starch storage in sheaths. Soluble sugar concentrations differed between mutant and WT in roots but not in shoots. Specifically, the hexose: sucrose ratio was 50% lower in the roots of the mutant, possibly indicating low invertase activity. Furthermore, two OsCIN genes coding for cell wall invertases were not expressed in roots, and others were expressed weakly. This was interpreted as natural silencing via sugar signalling. In summary, the authors attributed the majority of observed allometric and metabolic modifications in the mutant to an extreme assimilate shortage caused by hastened shoot organogenesis and inefficient leaf morphology.

Mots-clés Agrovoc : Oryza sativa, mutant, développement biologique, feuille, dimension, plante sauvage, métabolisme des glucides, fructofuranosidase, photosynthèse, modèle végétal

Mots-clés complémentaires : Sink effect

Classification Agris : F62 - Physiologie végétale - Croissance et développement
F30 - Génétique et amélioration des plantes

Champ stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

Auteurs et affiliations

• Luquet Delphine, CIRAD-AMIS-UPR Modélisation intégrative (FRA) ORCID: 0000-0002-2543-7140
• Song You Hong, CAAS (CHN)
• Elbelt Sonia, CIRAD-AMIS-UMR PIA (FRA)
• This Dominique, ENSAM [Ecole nationale supérieure agronomique de Montpellier] (FRA)
• Clément-Vidal Anne, CIRAD-CP-UMR BEPC (FRA)
• Perin Christophe, CIRAD-AMIS-UMR PIA (FRA) ORCID: 0000-0002-2469-310X
• Fabre Denis, CIRAD-AMIS-UPR Modélisation intégrative (FRA) ORCID: 0000-0002-6222-2587
• Dingkuhn Michaël, CIRAD-AMIS-UPR Modélisation intégrative (FRA)

Source : Cirad - Agritrop (https://agritrop.cirad.fr/536373/)

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