The mechanism of bud dehyperhydricity by the method of 'starvation drying combined with AgNO3' in Lycium ruthenicum

Abstract

Micropropagation is very important for rapid clonal propagation and scientific research of woody plants. However, the micropropagated materials usually show hyperhydricity, which seriously hinders application of the micropropagation. Lycium ruthenicum is an important species of eco-economic forests. Herein, treatment of 'starvation and drying combined with 30 μM AgNO3' (SDCAg+) removed serious hyperhydricity of L. ruthenicum buds regenerated from its green-inflorescence-explants, and then gene expression, metabolites of various phytohormones, chloroplasts, chlorophyll (Chl) and total soluble proteins of the hyperhydric and dehyperhydric leaves were compared and analyzed. The results suggested that the SDCAg+ treatment might remove hyperhydricity of L. ruthenicum through: reducing water uptake; increasing water loss; up-regulating the expression of chloroplast-ribosomal-protein genes from nuclear genome; down-regulating the expression of cytoplasmic-ribosomal-protein genes; up-regulating the synthesis of the total soluble proteins; restoring the lamellar structure of chloroplast grana and matrix; improving Chl synthesis and reducing Chl metabolism; increasing expression of light-harvesting Chl protein complex genes and content of Chla and b; up-regulating both photosynthesis and starch and sucrose metabolism KEGG pathways; up-regulating abscisic acid, salicylic acid and their signaling; down-regulating cytokinin, jasmonic acid, jasmonoyl-l-isoleucine and their signaling. Also, the above events interact to form a regulatory network of dehyperhydricity by SDCAg+ treatment. Overall, the study indicated key genes/pathways and physiological/subcellular changes involved in dehyperhydricity and then established a dehyperhydric mechanism model of L. ruthenicum. This not only proposed clues for preventing or removing hyperhydricity but also laid foundations for molecular breeding of L. ruthenicum and other species.

Keywords: RNA-Seq; black wolfberry; phytohormone metabolome; ribosome; strigolactone; vitrification.