Expression of Chia4-Pa chitinase genes during somatic and zygotic embryo development in Norway spruce (Picea abies): similarities and differences between gymnosperm and angiosperm class IV chitinases.
The developmental pathway of somatic embryogenesis in Norway spruce involves proliferation of proembryogenic masses (PEMs), PEM-to-somatic embryo transition and further development of the somatic embryos. It has previously been shown that extracellular signal molecules, including arabinogalactan proteins, lipo-chitooligosaccharides and chitinases, regulate somatic embryogenesis. The Chia4-Pa1 gene from Norway spruce is described here. The Chia4-Pa1 encodes a typical basic class IV chitinase, although the intron-exon organization of this gymnosperm chitinase is different from that in angiosperm class IV chitinases. The Chia4-Pa1 belongs to a small gene family with highly similar members, and the expression pattern of Chia4-Pa1 cannot be distinguished from that of other Chia4-Pa members. Upon withdrawal of plant growth regulators, i.e. during a treatment that stimulates PEM-to-somatic embryo transition and massive programmed cell death, a significant increase in transcription and translation of Chia4-Pa genes takes place. The expression pattern analysis revealed that Chia4-Pa genes are expressed in a subpopulation of proliferating cells and at the base of the somatic embryo. Furthermore, in seeds, Chia4-Pa genes are expressed in the megagametophyte in the single cell-layered zone surrounding the corrosion cavity. Taken together these results suggest that the Chia4-Pa expressing cells have a megagametophyte signalling function and that CHIA4-Pa stimulates programmed cell death and promotes PEM-to-somatic embryo transition.
Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Box 7080, SE-75007 Uppsala, Sweden. Malgorzata.Wiweger@vbsg.slu.se
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M
Wiweger
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Farbos
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M
Ingouff
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Lagercrantz
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Von Arnold
D001483:Base Sequence; D002688:Chitinases / Q000235:genetics*; D032462:Cycadopsida / Q000145:classification / Q000201:enzymology* / Q000254:growth & development; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D017403:In Situ Hybridization; D007527:Isoenzymes / Q000235:genetics; D019684:Magnoliopsida / Q000145:classification / Q000201:enzymology* / Q000254:growth & development; D010802:Phylogeny; D028222:Picea / Q000145:classification / Q000201:enzymology* / Q000254:growth & development; D012333:RNA, Messenger / Q000235:genetics
D018076:DNA, Complementary; D018744:DNA, Plant; D007527:Isoenzymes; D012333:RNA, Messenger; D002688:Chitinases