- Email: [email protected]
Lateral root emergence: A paradigm for cell signaling in plants
S144
Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S139–S147
C1/P4.20 Lateral root emergence: A paradigm for cell signaling in plants B. Peret (University of Nottingham); L. Laplaze (IRD); R. Swarup (University of Nottingham); M.J. Bennett (University of Nottingham)
Lateral roots originate deep within the parental root from a small number of founder cells at the periphery of the vascular tissues and must emerge through intervening layers of tissues. Despite its importance to the integrity of the root system, little is known about the regulation of lateral root emergence. Our study reveals that lateral root emergence is a highly regulated process involving the active participation of cells in both new lateral root primordia and the parental root. The hormone auxin originating from the developing lateral root appears to act as a local inductive signal which reprograms adjacent cells. Auxin induces the expression of a previously uncharacterized auxin influx carrier LAX3 in cortical and epidermal cells directly overlaying new primordia. Increased LAX3 activity reinforces the auxin-dependent induction of a selection of cell wall remodelling enzymes, promoting cell separation in advance of developing lateral root primordia. doi:10.1016/j.cbpa.2008.04.359
C1/P4.21 Signalling in the Arabidopsis root meristem K. Lindsey (Durham University); S. Casson, (University of Bristol); J. Topping (Durham University) The patterning and maintenance of the root meristem in Arabidopsis is the consequence of interactions between hormones and overlapping transcription factors. Radial pattern is established by interactions between SCARECROW (SCR) and SHORT-ROOT (SHR), both members of the GRAS transcription factor family. Both SCR and SHR proteins are also found in the quiescent centre (QC), a group of slowly dividing cells in the meristem that play a critical role in maintaining the undifferentiated state of the surrounding stem cells. The distribution of auxin by the AUX1 and PIN proteins is essential to maintain pattern. The transcription factors PLETHORA1 and 2 (PLT1 and 2) are activated by auxin in the QC and in the surrounding stem cell niche, overlapping with SCR and SHR. plt1 plt2 double mutants cannot specify the QC and so cannot maintain stem cell identity. This is consistent with a model for a combinatorial role for these transcription factors in controlling stem cell identity and activity in the root meristem, and in response to auxin. Here we will describe the analysis of the STL1 gene, a novel gene in Arabidopsis. STL1 expression initiates early in embryogenesis and was identified using laser-capture microdissection and microarray analysis of developing embryos. It is required for both the correct patterning of the embryo and root meristem but also maintenance of meristem activity. STL1 activity appears to be independent of PLT gene activity and auxin but is required to establish a correct auxin maximum and PLT gene expression. doi:10.1016/j.cbpa.2008.04.360
C1/P4.22 Signalling to programmed cell death in self-incompatible pollen M. Bosch, B. de Graaf, N. Poulter, S. Vatovec, S. Li, V. Franklin-Tong (University of Birmingham)
Many higher plants use self incompatibility (SI) to prevent selffertilization. In Papaver rhoeas, the rejection of “self” pollen involves a Ca2+-dependent signalling network that triggers programmed cell death (PCD), providing a neat way to get rid of unwanted incompatible (“self”) pollen. Several SI-induced events have been identified, including: rapid depolymerization of the actin and microtubule cytoskeleton (Snowman et al., 2002; Poulter et al., 2008); phosphorylation of a soluble inorganic pyrophosphatase (Rudd et al., 1996; de Graaf et al., 2006); activation of a MAPK, p56 (Rudd et al., 2003; Li et al., 2007), and PCD, which involves several caspase-like activities, including a DEVDase, VEIDase and a LEVDase (Bosch and Franklin-Tong, 2007; Thomas and Franklin-Tong, 2004). PCD provides a precise mechanism for the specific destruction of “self” pollen. Our focus recently has been on beginning to attempt to understand how the signalling networks involved in SI-mediated PCD are integrated. I will present recent data providing evidence for actin, microtubules and MAPK signalling to activate caspase-like activities, resulting in PCD.
References Snowman, B.N., Kovar, D.R., Shevchenko, G., Franklin-Tong, V.E., Staiger, C.J., 2002. Plant Cell 14, 2613–2626 2002. Poulter, N.S., Vatovec, S., Franklin-Tong, V.E., 2008. Plant Physiol. 146, 1358–1367. Rudd, J.J., Franklin, F.C.H., Lord, J.M., Franklin-Tong, V.E., 1996. Plant Cell 8, 713–724. de Graaf, B.H.J., Rudd, J.J., Wheeler, M.J., Perry, R.M., Bell, E.M., Osman, K., Franklin, F.C.H., Franklin-Tong, V.E., 2006. Nature 444, 490–493. Rudd, J.J., Osman, K., Franklin, F.C.H., Franklin-Tong, V.E., 2003. FEBS Lett. 547, 223–227. Li, S., Samaj, J., Franklin-Tong, V.E., 2007. Plant Physiol. 145, 236–245. Bosch, M., Franklin-Tong, V.E., 2007. PNAS USA 104, 18327–18332. Thomas, S.G., Franklin-Tong, V.E., 2004. Nature 429, 305–309. doi:10.1016/j.cbpa.2008.04.361
C1/P4.23 Control of stomatal development J. Gray, L. Hunt (University of Sheffield) Stomata are pores on the aerial surfaces of plants that facilitate the exchange of CO2 and water vapour with the environment. Each pore is formed by a pair of guard cells which expand and contract in response to environmental signals, to control pore aperture and water loss. The number of stomata that develop on the leaf surface is also under environmental control with, for example, less stomata being formed on plants grown at elevated CO2 levels. Studies of Arabidopsis thaliana mutants have identified a number of genes controlling the pattern of cell divisions leading to stomatal formation and patterning. From analysis of plants with altered expression of these genes it appears that an extracellular signaling pathway involving peptides and processing proteases in combination with LRR receptor complexes activate an intracellular MAPK cascade that inhibits entry to the stomatal lineage by restricting the formation and division of meristemoids. Recent results suggesting that secretory peptides, expressed early in leaf development, limit the capacity of cells to enter the stomatal lineage will be discussed.
doi:10.1016/j.cbpa.2008.04.362
Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S139–S147
C1/P4.20 Lateral root emergence: A paradigm for cell signaling in plants B. Peret (University of Nottingham); L. Laplaze (IRD); R. Swarup (University of Nottingham); M.J. Bennett (University of Nottingham)
Lateral roots originate deep within the parental root from a small number of founder cells at the periphery of the vascular tissues and must emerge through intervening layers of tissues. Despite its importance to the integrity of the root system, little is known about the regulation of lateral root emergence. Our study reveals that lateral root emergence is a highly regulated process involving the active participation of cells in both new lateral root primordia and the parental root. The hormone auxin originating from the developing lateral root appears to act as a local inductive signal which reprograms adjacent cells. Auxin induces the expression of a previously uncharacterized auxin influx carrier LAX3 in cortical and epidermal cells directly overlaying new primordia. Increased LAX3 activity reinforces the auxin-dependent induction of a selection of cell wall remodelling enzymes, promoting cell separation in advance of developing lateral root primordia. doi:10.1016/j.cbpa.2008.04.359
C1/P4.21 Signalling in the Arabidopsis root meristem K. Lindsey (Durham University); S. Casson, (University of Bristol); J. Topping (Durham University) The patterning and maintenance of the root meristem in Arabidopsis is the consequence of interactions between hormones and overlapping transcription factors. Radial pattern is established by interactions between SCARECROW (SCR) and SHORT-ROOT (SHR), both members of the GRAS transcription factor family. Both SCR and SHR proteins are also found in the quiescent centre (QC), a group of slowly dividing cells in the meristem that play a critical role in maintaining the undifferentiated state of the surrounding stem cells. The distribution of auxin by the AUX1 and PIN proteins is essential to maintain pattern. The transcription factors PLETHORA1 and 2 (PLT1 and 2) are activated by auxin in the QC and in the surrounding stem cell niche, overlapping with SCR and SHR. plt1 plt2 double mutants cannot specify the QC and so cannot maintain stem cell identity. This is consistent with a model for a combinatorial role for these transcription factors in controlling stem cell identity and activity in the root meristem, and in response to auxin. Here we will describe the analysis of the STL1 gene, a novel gene in Arabidopsis. STL1 expression initiates early in embryogenesis and was identified using laser-capture microdissection and microarray analysis of developing embryos. It is required for both the correct patterning of the embryo and root meristem but also maintenance of meristem activity. STL1 activity appears to be independent of PLT gene activity and auxin but is required to establish a correct auxin maximum and PLT gene expression. doi:10.1016/j.cbpa.2008.04.360
C1/P4.22 Signalling to programmed cell death in self-incompatible pollen M. Bosch, B. de Graaf, N. Poulter, S. Vatovec, S. Li, V. Franklin-Tong (University of Birmingham)
Many higher plants use self incompatibility (SI) to prevent selffertilization. In Papaver rhoeas, the rejection of “self” pollen involves a Ca2+-dependent signalling network that triggers programmed cell death (PCD), providing a neat way to get rid of unwanted incompatible (“self”) pollen. Several SI-induced events have been identified, including: rapid depolymerization of the actin and microtubule cytoskeleton (Snowman et al., 2002; Poulter et al., 2008); phosphorylation of a soluble inorganic pyrophosphatase (Rudd et al., 1996; de Graaf et al., 2006); activation of a MAPK, p56 (Rudd et al., 2003; Li et al., 2007), and PCD, which involves several caspase-like activities, including a DEVDase, VEIDase and a LEVDase (Bosch and Franklin-Tong, 2007; Thomas and Franklin-Tong, 2004). PCD provides a precise mechanism for the specific destruction of “self” pollen. Our focus recently has been on beginning to attempt to understand how the signalling networks involved in SI-mediated PCD are integrated. I will present recent data providing evidence for actin, microtubules and MAPK signalling to activate caspase-like activities, resulting in PCD.
References Snowman, B.N., Kovar, D.R., Shevchenko, G., Franklin-Tong, V.E., Staiger, C.J., 2002. Plant Cell 14, 2613–2626 2002. Poulter, N.S., Vatovec, S., Franklin-Tong, V.E., 2008. Plant Physiol. 146, 1358–1367. Rudd, J.J., Franklin, F.C.H., Lord, J.M., Franklin-Tong, V.E., 1996. Plant Cell 8, 713–724. de Graaf, B.H.J., Rudd, J.J., Wheeler, M.J., Perry, R.M., Bell, E.M., Osman, K., Franklin, F.C.H., Franklin-Tong, V.E., 2006. Nature 444, 490–493. Rudd, J.J., Osman, K., Franklin, F.C.H., Franklin-Tong, V.E., 2003. FEBS Lett. 547, 223–227. Li, S., Samaj, J., Franklin-Tong, V.E., 2007. Plant Physiol. 145, 236–245. Bosch, M., Franklin-Tong, V.E., 2007. PNAS USA 104, 18327–18332. Thomas, S.G., Franklin-Tong, V.E., 2004. Nature 429, 305–309. doi:10.1016/j.cbpa.2008.04.361
C1/P4.23 Control of stomatal development J. Gray, L. Hunt (University of Sheffield) Stomata are pores on the aerial surfaces of plants that facilitate the exchange of CO2 and water vapour with the environment. Each pore is formed by a pair of guard cells which expand and contract in response to environmental signals, to control pore aperture and water loss. The number of stomata that develop on the leaf surface is also under environmental control with, for example, less stomata being formed on plants grown at elevated CO2 levels. Studies of Arabidopsis thaliana mutants have identified a number of genes controlling the pattern of cell divisions leading to stomatal formation and patterning. From analysis of plants with altered expression of these genes it appears that an extracellular signaling pathway involving peptides and processing proteases in combination with LRR receptor complexes activate an intracellular MAPK cascade that inhibits entry to the stomatal lineage by restricting the formation and division of meristemoids. Recent results suggesting that secretory peptides, expressed early in leaf development, limit the capacity of cells to enter the stomatal lineage will be discussed.
doi:10.1016/j.cbpa.2008.04.362