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Summary: MicroRNA169 (miR169) has been implicated in multi‐stress regulation in annual species such as Arabidopsis, maize and rice. However, there is a lack of experimental functional and mechanistic studies of miR169 in plants, especially in perennial species, and its impact on plant growth and development remains unexplored. Creeping bentgrass (Agrostis stolonifera L.) is a C3 cool‐season perennial turfgrass of significant environmental and economic importance. In this study, we generated both miR169 overexpression and knockdown transgenic creeping bentgrass lines. We found that miR169 acts as a positive regulator in abiotic stress responses but is negatively associated with plant growth and development, playing multiple critical roles in the growth and environmental adaptation of creeping bentgrass. These roles include differentiated spatial hormone accumulation patterns associated with growth and stress accommodation, elevated antioxidant activity that alleviates oxidative damage induced by stress, ion‐channelling membrane components for maintaining homeostasis under saline conditions, and potential cross‐talks with stress‐regulating transcription factors such as AsHsfA and AsWRKYs. Our results unravel the role of miR169 in modulating plant development and stress responses in perennial grass species. This underlines the potential of manipulating miR169 to generate crop cultivars with desirable traits to meet diverse agricultural demands. [ABSTRACT FROM AUTHOR]

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1365-2745.2007.01216.x Byline: SERGIO R. ROILOA, PETER ALPERT, NISHANTH THARAYIL (*), GOVINDA HANCOCK, PRASANTA C. BHOWMIK (*) Keywords: adaptive plasticity; allocation to root and shoot; chlorophyll content; clonal growth; division of labour; environmental heterogeneity; Fragaria chiloensis; grassland; physiological integration; sand dune Abstract: Summary Unlike non-clonal plants, clonal plants can develop a division of labour in which connected ramets specialize to acquire different, locally abundant resources. This occurs as a plastic response to a patchy environment where two resources tend not to occur together and different ramets experience high availabilities of different resources. We hypothesized that if division of labour is an important advantage of clonal growth in such environments in nature, then clones from habitats where resource availabilities are negatively associated should show a greater capacity for division of labour than clones from habitats where resource availabilities are more uniform. To test this, we collected clones of Fragaria chiloensis from sand dune and grassland sites in each of three regions of the central coast of California, grew pairs of connected or severed ramets under low light and high N or under high light and low N, and measured leaf area, chlorophyll content and final dry mass. Given that previous work has indicated that high availabilities of light and N show a stronger tendency not to occur together in the dune than in the grassland sites, we expected that clones from dunes would show greater capacity for division of labour than clones from grasslands. Clones from dunes showed a greater capacity than clones from grasslands to specialize for acquisition of abundant N via high proportional mass of roots. Clones from the two types of habitats showed similar capacity to specialize for acquisition of abundant light via high leaf area and chlorophyll content of leaves. Specialization via leaf area and chlorophyll content took place mainly within the first half of the 60-day experiment. These results provide evidence that division of labour in a clonal plant has been selected for in natural habitats where high levels of different resources tend to be spatially separated. Results also show that division of labour can occur, not just via allocation of mass, but also via physiological traits, and that both morphological and physiological specialization can take place within a few weeks. Clonal plants dominate many habitats and include many highly invasive species. Division of labour is one of the most striking potential advantages of clonal growth, and is a remarkable instance of phenotypic plasticity in plants. This study further suggests that division of labour in clonal plants is an instance of adaptive plasticity and could therefore play a part in their widespread ecological success. Author Affiliation: (*)Department of Plant and Soil Sciences, University of Massachusetts, Amherst, MA 01003, USA Article History: Received 23 July 2006 Revision accepted 12 December 2006 Handling Editor: Michael Hutchings Article note: Correspondence and present address: Sergio R. Roiloa, Unit of Ecology, Faculty of Biology, University of Santiago de Compostela, 15782 Spain (fax +34 981 596904; e-mail srroiloa@usc.es).