Diverse chitinases are invoked during the activity-dormancy transition in spruce

Abstract

North temperate tree species such as white spruce (Picea glauca [Moench] Voss) have evolved strategies to protect themselves against abiotic and biotic stresses that trees encounter during the inclement winter months. Chitinases not only play well-documented roles in plant defense but also function during physiological and developmental preparations for overwintering, including growth cessation, cold and desiccation acclimation, and dormancy acquisition. Phylogenetic analysis of 31 white spruce and 52 Norway spruce chitinases identified genes falling into each of the five clusters, which sometimes-but not always-separated the different biochemical classes of chitinases. Digital expression profiling of white spruce and Norway spruce chitinases across multiple conditions revealed a range of spatiotemporal expression patterns. Transcript abundance profiling in buds, needles, stems, and roots by quantitative RT-PCR suggested roles for eight white spruce chitinases during the growth-to-dormancy transition. In silico analyses of these eight sequences suggested that two cluster 2/class I chitinases function as chitinolytic enzymes in the tree's constitutive defense arsenal during the winter months. A cluster 2/class I, cluster 2/class II, and cluster 1/ class IV chitinase each exhibit hallmarks of antifreeze proteins. Additionally, two cluster 2/class I chitinases and a cluster 1/ class IV chitinase may serve as vegetative storage proteins. One cluster 3/class II chitinase exhibited attributes suggesting that it is a chitinase-like gene functioning in cell wall synthesis. Taken together, our results imply that dormancy-associated chitinases act in concert to (1) confer protection against freezing injury, pests, and pathogens, (2) store nitrogen, and (3) promote cell maturation that precedes growth cessation.

Distinctive Gene Expression Patterns Define Endodormancy to Ecodormancy Transition in Apricot and Peach

“…Changes in cell wall structure and components are critical for the processes of growth and stress resistance (Zwiazek, 1991), and previous studies have shown the increase of cell wall formation and reactive oxygen species (ROS) signaling (Jian et al, 1997;Considine and Foyer, 2014) during bud dormancy. Chitinases were reported to be associated with protection against freezing and promote cell wall biosynthesis during dormancy in white spruce (González et al, 2015).…”

Modulation of Dormancy and Growth Responses in Reproductive Buds of Temperate Trees

“…Seasonal up-regulation of a dehydrin gene in bark tissue is lower and restricted to a shorter period in the evergrowing ( evg ) mutant of peach having a deletion in DAM genes, in concordance with its lower cold tolerance ( Arora et al, 1992 ; Arora and Wisniewski, 1994 ; Artlip et al, 1997 ). Diverse chitinases have been also suggested to act as antifreeze, storage, and defense proteins induced during the transition to dormancy in spruce ( González et al, 2015 ).…”

The humidity level matters during the desiccation of Norway spruce somatic embryos

“…Previously, a class I chitinase was induced by low temperature in mature white spruce somatic embryos (Gao et al, 2022), but was suppressed by wounding (Hietala et al, 2004). Chitinases of different classes were also differentially expressed in P. glauca during the transition between seasonal activity and dormancy (González et al, 2015).…”