Plants respond to environmental stresses through controlled stem cell maintenance and meristem activity. One level of transcriptional control is RNA alternative splicing. However the mechanistic link between stress, meristem function and RNA splicing is poorly understood. The MERISTEM-DEFECTIVE (MDF)/DEFECTIVELY ORGANIZED TRIBUTARIES (DOT2) gene of Arabidopsis encodes a SR-related family protein, required for meristem function and leaf vascularization, and is the likely orthologue of the human SART1 and yeast snu66 splicing factors. MDF is required for the correct splicing and expression of key transcripts associated with root meristem function. We identified RSZ33 and ACC1, both known to regulate cell patterning, as splicing targets required for MDF function in the meristem. MDF expression is modulated by osmotic and cold stress, associated with differential splicing and specific isoform accumulation and shuttling between nucleus and cytosol, and acts in part via a splicing target SR34. We propose a model in which MDF controls splicing in the root meristem to promote stemness and repress stress response and cell differentiation pathways.

Deuteropolystyrene has been functionalised at each end by fluorosilane groups, the polymer obtained had a relative molar mass of 98 ×103. Thin films of this polymer mixed with unfunctionalised hydrogenous polystyrene have been prepared and the blends annealed to equilibrium at 413 K. The distribution of the end functionalised deuteropolymer was obtained by neutron reflectometry and a range of molecular weights of the hydrogenous polystyrene matrix has been used. In all cases the deutero polystyrene was preferentially located at the air-polymer interface to an extent which was far greater than that for unfunctionalised deutero polystyrene in the same hydrogenous matrices. From the near surface depth profiles obtained, the surface excess, surface volume fraction and thickness of the end functionalised deuteropolystyrene rich layer have been obtained as a function of the equilibrium concentration of end functionalised deuteropolystyrene. These parameters have been compared with the predictions of scaling theory for brush like layers of polymers attached to a surface. The surface layer thickness and average volume fraction of the surface layer display stretched wet brush behaviour which is not expected for end functionalised polymers on the basis of the molecular weights explored. The possibility that local grafting densities are significantly higher than the average value is discussed. The shape of the near surface depth profile has been fitted using a self consistent field theory using the “sticking energy” of the fluorosilane groups as the only adjustable parameter. Fits of reasonable quality were obtained and using this sticking energy the surface volume fractions and normalised surface excess parameters have been calculated and compared with those obtained experimentally. Good agreement between surface volume fractions is obtained, but the agreement between normalised surface excess values becomes increasingly worse as the relative molar mass of the hydrogenous matrix increases

Plants respond to environmental stresses through controlled stem cell maintenance and meristem activity. One level of gene regulation is RNA alternative splicing. However the mechanistic link between stress, meristem function and RNA splicing is poorly understood. The MERISTEM-DEFECTIVE (MDF)/DEFECTIVELY ORGANIZED TRIBUTARIES (DOT2) gene of Arabidopsis encodes a SR-related family protein, required for meristem function and leaf vascularization, and is the likely orthologue of the human hSART1 and yeast Snu66 splicing factors. MDF is required for the correct splicing and expression of key transcripts associated with root meristem function. We identified RSZ33 and ACC1, both known to regulate cell patterning, as splicing targets required for MDF function in the meristem. MDF expression is modulated by osmotic and cold stress, associated with differential splicing and specific isoform accumulation and shuttling between nucleus and cytosol, and acts in part via a splicing target SR34. We propose a model in which MDF controls splicing in the root meristem to promote stemness and repress stress response, cell differentiation and cell death pathways.