Endochitinase and beta-1,3-glucanase genes are developmentally regulated during somatic embryogenesis in Picea glauca

Two cDNAs isolated from white spruce [Picea glauca (Moench) Voss] somatic embryos, are predicted to encode a basic class IV chitinase and a beta-1,3-glucanase, respectively corresponding to genes PgChi-1 and PgGlu-1. Each represents a multigene family in spruce. Transcripts homologous to PgChi-1 or PgGlu-1 genes were highly abundant in embryogenic tissues and gradually decreased after tissues were placed on abscisic acid-containing maturation medium, with lowest abundance in globular embryos. Transcripts related to PgGlu-1 became highly abundant again in early cotyledonary embryos but decreased thereafter, whereas transcripts related to PgChi-1 were also highly abundant in late cotyledonary embryos and plantlets in vitro; transcripts were either low (PgChi-1) or were not detectable (PgGlu-1) in needles. Wounding, drying and flooding stresses enhanced PgChi-1- and PgGlu-1-related gene expression. Fungal cell wall suspension enhanced PgGlu-1-related transcript accumulation, but reduced PgChi-1-related transcript abundance within 24 h. PgChi-1 and PgGlu-1 and their homologues may have roles in plant defense, and possibly developmental roles during spruce somatic embryo maturation.