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Differential regulation of Knotted1-like genes during establishment of the shoot apical meristem in Norway spruce (Picea abies).

Larsson E, Sitbon F, von Arnold S - Plant Cell Rep. (2012)

Bottom Line: This was made both under normal embryo development and under conditions of reduced SAM formation by treatment with the polar auxin transport inhibitor NPA.Concomitantly with the formation of an embryonic SAM, the HBK2 and HBK4 genes displayed a significant up-regulation that was delayed by NPA treatment.Together, the results suggest that HBK2 and HBK4 exert similar functions related to the SAM differentiation and somatic embryo development in Norway spruce, while HBK1 and HBK3 have more general functions during embryo development.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences, P. O. Box 7080, 75007 Uppsala, Sweden. emma.larsson@slu.se

ABSTRACT
Establishment of the shoot apical meristem (SAM) in Arabidopsis embryos requires the KNOXI transcription factor SHOOT MERISTEMLESS. In Norway spruce (Picea abies), four KNOXI family members (HBK1, HBK2, HBK3 and HBK4) have been identified, but a corresponding role in SAM development has not been demonstrated. As a first step to differentiate between the functions of the four Norway spruce HBK genes, we have here analyzed their expression profiles during the process of somatic embryo development. This was made both under normal embryo development and under conditions of reduced SAM formation by treatment with the polar auxin transport inhibitor NPA. Concomitantly with the formation of an embryonic SAM, the HBK2 and HBK4 genes displayed a significant up-regulation that was delayed by NPA treatment. In contrast, HBK1 and HBK3 were up-regulated prior to SAM formation, and their temporal expression was not affected by NPA. Ectopic expression of the four HBK genes in transgenic Arabidopsis plants further supported similar functions of HBK2 and HBK4, distinct from those of HBK1 and HBK3. Together, the results suggest that HBK2 and HBK4 exert similar functions related to the SAM differentiation and somatic embryo development in Norway spruce, while HBK1 and HBK3 have more general functions during embryo development.

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Quantitative real-time PCR analysis of HBK1 (a), HBK2 (b), HBK3 (c) and HBK4 (d) mRNA levels during eight consecutive stages of control (dark bars) and NPA-treated (light bars) somatic embryos of Norway spruce. Embryos from stage 3 and later were sampled individually. Expression values are relative to the expression of each gene at stage 1, normalized against three reference genes. The expression levels are mean values of three biological replicates, each analyzed in triplicate and presented in a logarithmic scale. Error bars indicate SEM of biological replicates. Asterisks indicate a difference between stage 1 and later stages of control cultures, significant at *p < 0.05 or **p < 0.01. Circles indicate a significant difference (p < 0.01) between control and NPA-treated embryos at the stages indicated
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Fig2: Quantitative real-time PCR analysis of HBK1 (a), HBK2 (b), HBK3 (c) and HBK4 (d) mRNA levels during eight consecutive stages of control (dark bars) and NPA-treated (light bars) somatic embryos of Norway spruce. Embryos from stage 3 and later were sampled individually. Expression values are relative to the expression of each gene at stage 1, normalized against three reference genes. The expression levels are mean values of three biological replicates, each analyzed in triplicate and presented in a logarithmic scale. Error bars indicate SEM of biological replicates. Asterisks indicate a difference between stage 1 and later stages of control cultures, significant at *p < 0.05 or **p < 0.01. Circles indicate a significant difference (p < 0.01) between control and NPA-treated embryos at the stages indicated

Mentions: HBK1 was expressed in proliferating PEMs and the expression was significantly up-regulated from stage 3 and then down-regulated in mature embryos (Fig. 2a). The relative expression of HBK3 (Fig. 2c) was similar to that of HBK1, although HBK3 became significantly up-regulated first at stage 4 and then remained at a high expression level. Treatment with NPA did not significantly alter the expression of either gene. These results show that the accumulation of both HBK1 and HBK3 mRNA precedes the differentiation of the SAM. However, since NPA-treated embryos lack a visible SAM (Larsson et al. 2008), the absence of an NPA-response on HBK1 and HBK3 expression suggests that the genes are not specifically related to SAM establishment, and thus have a more general role in embryo development.Fig. 2


Differential regulation of Knotted1-like genes during establishment of the shoot apical meristem in Norway spruce (Picea abies).

Larsson E, Sitbon F, von Arnold S - Plant Cell Rep. (2012)

Quantitative real-time PCR analysis of HBK1 (a), HBK2 (b), HBK3 (c) and HBK4 (d) mRNA levels during eight consecutive stages of control (dark bars) and NPA-treated (light bars) somatic embryos of Norway spruce. Embryos from stage 3 and later were sampled individually. Expression values are relative to the expression of each gene at stage 1, normalized against three reference genes. The expression levels are mean values of three biological replicates, each analyzed in triplicate and presented in a logarithmic scale. Error bars indicate SEM of biological replicates. Asterisks indicate a difference between stage 1 and later stages of control cultures, significant at *p < 0.05 or **p < 0.01. Circles indicate a significant difference (p < 0.01) between control and NPA-treated embryos at the stages indicated
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3351593&req=5

Fig2: Quantitative real-time PCR analysis of HBK1 (a), HBK2 (b), HBK3 (c) and HBK4 (d) mRNA levels during eight consecutive stages of control (dark bars) and NPA-treated (light bars) somatic embryos of Norway spruce. Embryos from stage 3 and later were sampled individually. Expression values are relative to the expression of each gene at stage 1, normalized against three reference genes. The expression levels are mean values of three biological replicates, each analyzed in triplicate and presented in a logarithmic scale. Error bars indicate SEM of biological replicates. Asterisks indicate a difference between stage 1 and later stages of control cultures, significant at *p < 0.05 or **p < 0.01. Circles indicate a significant difference (p < 0.01) between control and NPA-treated embryos at the stages indicated
Mentions: HBK1 was expressed in proliferating PEMs and the expression was significantly up-regulated from stage 3 and then down-regulated in mature embryos (Fig. 2a). The relative expression of HBK3 (Fig. 2c) was similar to that of HBK1, although HBK3 became significantly up-regulated first at stage 4 and then remained at a high expression level. Treatment with NPA did not significantly alter the expression of either gene. These results show that the accumulation of both HBK1 and HBK3 mRNA precedes the differentiation of the SAM. However, since NPA-treated embryos lack a visible SAM (Larsson et al. 2008), the absence of an NPA-response on HBK1 and HBK3 expression suggests that the genes are not specifically related to SAM establishment, and thus have a more general role in embryo development.Fig. 2

Bottom Line: This was made both under normal embryo development and under conditions of reduced SAM formation by treatment with the polar auxin transport inhibitor NPA.Concomitantly with the formation of an embryonic SAM, the HBK2 and HBK4 genes displayed a significant up-regulation that was delayed by NPA treatment.Together, the results suggest that HBK2 and HBK4 exert similar functions related to the SAM differentiation and somatic embryo development in Norway spruce, while HBK1 and HBK3 have more general functions during embryo development.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences, P. O. Box 7080, 75007 Uppsala, Sweden. emma.larsson@slu.se

ABSTRACT
Establishment of the shoot apical meristem (SAM) in Arabidopsis embryos requires the KNOXI transcription factor SHOOT MERISTEMLESS. In Norway spruce (Picea abies), four KNOXI family members (HBK1, HBK2, HBK3 and HBK4) have been identified, but a corresponding role in SAM development has not been demonstrated. As a first step to differentiate between the functions of the four Norway spruce HBK genes, we have here analyzed their expression profiles during the process of somatic embryo development. This was made both under normal embryo development and under conditions of reduced SAM formation by treatment with the polar auxin transport inhibitor NPA. Concomitantly with the formation of an embryonic SAM, the HBK2 and HBK4 genes displayed a significant up-regulation that was delayed by NPA treatment. In contrast, HBK1 and HBK3 were up-regulated prior to SAM formation, and their temporal expression was not affected by NPA. Ectopic expression of the four HBK genes in transgenic Arabidopsis plants further supported similar functions of HBK2 and HBK4, distinct from those of HBK1 and HBK3. Together, the results suggest that HBK2 and HBK4 exert similar functions related to the SAM differentiation and somatic embryo development in Norway spruce, while HBK1 and HBK3 have more general functions during embryo development.

Show MeSH
Related in: MedlinePlus