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- Filonova, LH, et al.
(författare)
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Two waves of programmed cell death occur during formation and development of somatic embryos in the gymnosperm, Norway spruce
- 2000
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Ingår i: Journal of cell science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 113113 Pt 24:24, s. 4399-4411
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Tidskriftsartikel (refereegranskat)abstract
- In the animal life cycle, the earliest manifestations of programmed cell death (PCD) can already be seen during embryogenesis. The aim of this work was to determine if PCD is also involved in the elimination of certain cells during plant embryogenesis. We used a model system of Norway spruce somatic embryogenesis, which represents a multistep developmental pathway with two broad phases. The first phase is represented by proliferating proembryogenic masses (PEMs). The second phase encompasses development of somatic embryos, which arise from PEMs and proceed through the same sequence of stages as described for their zygotic counterparts. Here we demonstrate two successive waves of PCD, which are implicated in the transition from PEMs to somatic embryos and in correct embryonic pattern formation, respectively. The first wave of PCD is responsible for the degradation of PEMs when they give rise to somatic embryos. We show that PCD in PEM cells and embryo formation are closely interlinked processes, both stimulated upon withdrawal or partial depletion of auxins and cytokinins. The second wave of PCD eliminates terminally differentiated embryo-suspensor cells during early embryogeny. During the dismantling phase of PCD, PEM and embryo-suspensor cells exhibit progressive autolysis, resulting in the formation of a large central vacuole. Autolytic degradation of the cytoplasm is accompanied by lobing and budding-like segmentation of the nucleus. Nuclear DNA undergoes fragmentation into both large fragments of about 50 kb and multiples of approximately 180 bp. The tonoplast rupture is delayed until lysis of the cytoplasm and organelles, including the nucleus, is almost complete. The protoplasm then disappears, leaving a cellular corpse represented by only the cell wall. This pathway of cell dismantling suggests overlapping of apoptotic and autophagic types of PCD during somatic embryogenesis in Norway spruce.
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- Hjortswang, H I, et al.
(författare)
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KNOTTED1-like homeobox genes of a gymnosperm, Norway spruce, expressed during somatic embryogenesis
- 2002
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Ingår i: Plant physiology and biochemistry (Paris). - 0981-9428 .- 1873-2690. ; 40:10, s. 837-843
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Tidskriftsartikel (refereegranskat)abstract
- Two Norway spruce (Picea abies (L.) Karst.) genes belonging to class I of the KNOTTED1-like homeobox (KNOX) genes, HBK2 and HBK3, were cloned with PCR-based methods. The expression of these and a previously characterised related gene, HBK1, in different organs and during somatic embryogenesis was studied with RTPCR. Transcripts of all three genes were detected in stems, roots and in cone buds, but not in needles. HBK1 and HBK3 are expressed throughout development in a normal cell line with embryogenic potential and in a cell line unable to form somatic embryos. HBK2 is expressed in the normal cell line, but not in the developmentally arrested cell line. This suggests that the HBK2 gene is involved in the somatic embryo development.
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- Wadenback, J., et al.
(författare)
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Variation in content and composition of lignin in young wood of Norway spruce
- 2004
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Ingår i: Holzforschung. - 0018-3830 .- 1437-434X. ; 58:2, s. 107-115
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Tidskriftsartikel (refereegranskat)abstract
- Lignin content and composition are important traits in several tree breeding programs, but very little is known about their natural variation. This study compares the lignin content in 1-yearold plants and 9-yearold trees of Norway spruce belonging to the same fullsib families. It is shown that the lignin content, according to the modified acetyl bromide method, does not vary significantly within or among the different fullsib families either as plants or as young trees. There is, however, on average 4.0% higher lignin content (31.4% versus 27.4%) and lower standard error for the trees than for the plants. The number of C9-units/g(-1) lignin, analyzed by thioacidolysis, ranges from 516 to 1186 mummol C9-units/g(-1) lignin in plants and from 716 to 953 mumol C9-units/g(-1) lignin in trees, with no significant differences among the families. However, the extent of change in C9-units/g(-1) lignin varies among the families with age. The ratio of erythro and threo stereoisomers does not vary significantly among the families. However, the ratio changes differently with age among the families similar to the C9-units g(-1) lignin. Additionally, the content of phydroxyphenyl (H) lignin is 0.6% higher in the trees than in the plants (1.4% versus 0.8%), estimated indirectly from GCMS data by a novel subtractive technique, indicating a higher degree of compression wood in the young trees. In conclusion, the amount and composition of lignin does not vary within or among the families at the same age. However, the amount of lignin increases with age while the change in lignin composition varies between family and age.
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