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Dumais, J. (2013). Modes of deformation of walled cells. J. Exp. Bot., 64(15), 4681–4695.
Abstract: The bewildering morphological diversity found in cells is one of the starkest illustrations of lifes ability to self-organize. Yet the morphogenetic mechanisms that produce the multifarious shapes of cells are still poorly understood. The shared similarities between the walled cells of prokaryotes, many protists, fungi, and plants make these groups particularly appealing to begin investigating how morphological diversity is generated at the cell level. In this review, I attempt a first classification of the different modes of surface deformation used by walled cells. Five modes of deformation were identified: inextensional bending, equi-area shear, elastic stretching, processive intussusception, and chemorheological growth. The two most restrictive modesuinextensional and equi-area deformationsuare embodied in the exine of pollen grains and the wall-like pellicle of euglenoids, respectively. For these modes, it is possible to express the deformed geometry of the cell explicitly in terms of the undeformed geometry and other easily observable geometrical parameters. The greatest morphogenetic power is reached with the processive intussusception and chemorheological growth mechanisms that underlie the expansive growth of walled cells. A comparison of these two growth mechanisms suggests a possible way to tackle the complexity behind wall growth.
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Kraiser, T., Gras, D. E., Gutierrez, A. G., Gonzalez, B., & Gutierrez, R. A. (2011). A holistic view of nitrogen acquisition in plants. J. Exp. Bot., 62(4), 1455–1466.
Abstract: Nitrogen (N) is the mineral nutrient required in the greatest amount and its availability is a major factor limiting growth and development of plants. As sessile organisms, plants have evolved different strategies to adapt to changes in the availability and distribution of N in soils. These strategies include mechanisms that act at different levels of biological organization from the molecular to the ecosystem level. At the molecular level, plants can adjust their capacity to acquire different forms of N in a range of concentrations by modulating the expression and function of genes in different N uptake systems. Modulation of plant growth and development, most notably changes in the root system architecture, can also greatly impact plant N acquisition in the soil. At the organism and ecosystem levels, plants establish associations with diverse microorganisms to ensure adequate nutrition and N supply. These different adaptive mechanisms have been traditionally discussed separately in the literature. To understand plant N nutrition in the environment, an integrated view of all pathways contributing to plant N acquisition is required. Towards this goal, in this review the different mechanisms that plants utilize to maintain an adequate N supply are summarized and integrated.
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Loyola, R., Herrera, D., Mas, A., Wong, D. C. J., Holl, J., Cavallini, E., et al. (2016). The photomorphogenic factors UV-B RECEPTOR 1, ELONGATED HYPOCOTYL 5, and HY5 HOMOLOGUE are part of the UV-B signalling pathway in grapevine and mediate flavonol accumulation in response to the environment. J. Exp. Bot., 67(18), 5429–5445.
Abstract: By performing molecular studies coupled to radiation experiments and in silico systems analyses, we have ascertained the role of the grapevine UV-B receptor and two HY5 homologues in regulating flavonol synthesis.Grapevine (Vitis vinifera L.) is a species well known for its adaptation to radiation. However, photomorphogenic factors related to UV-B responses have not been molecularly characterized. We cloned and studied the role of UV-B RECEPTOR (UVR1), ELONGATED HYPOCOTYL 5 (HY5), and HY5 HOMOLOGUE (HYH) from V. vinifera. We performed gene functional characterizations, generated co-expression networks, and tested them in different environmental conditions. These genes complemented the Arabidopsis uvr8 and hy5 mutants in morphological and secondary metabolic responses to radiation. We combined microarray and RNA sequencing (RNA-seq) data with promoter inspections to identify HY5 and HYH putative target genes and their DNA binding preferences. Despite sharing a large set of common co-expressed genes, we found different hierarchies for HY5 and HYH depending on the organ and stress condition, reflecting both co-operative and partially redundant roles. New candidate UV-B gene markers were supported by the presence of HY5-binding sites. These included a set of flavonol-related genes that were up-regulated in a HY5 transient expression assay. We irradiated in vitro plantlets and fruits from old potted vines with high and low UV-B exposures and followed the accumulation of flavonols and changes in gene expression in comparison with non-irradiated conditions. UVR1, HY5, and HYH expression varied with organ, developmental stage, and type of radiation. Surprisingly, UVR1 expression was modulated by shading and temperature in berries, but not by UV-B radiation. We propose that the UV-B response machinery favours berry flavonol accumulation through the activation of HY5 and HYH at different developmental stages at both high and low UV-B exposures.
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