Comparative transcriptomic profiles of Paulownia catalpifolia under different degrees of chilling stress during the seedling stage.

BACKGROUND: Paulownia, an ecologically and economically valuable plant species native to China, is notable for its excellent timber quality and strong adaptability. Among them, Paulownia catalpifolia displays the ability to survive in cold climate, a trait associated with northern China. Yet, the molecular information for its cold-tolerance has not been explored. This study was to investigate the changes in physiological indices and transcript levels of P. catalpifolia following cold exposure, which could provide evidence for revealing whether there were differences in the genetic basis of inducing physiological perturbations between moderate low temperature (MLT) and extreme low temperature (ELT). RESULTS: The detection of physiological indices under diverse degrees of chilling stress showed similar patterns of alteration. Enhanced accumulation of osmoregulatory substances, such as soluble sugar and soluble protein, were more conducive under ELT compared to MLT in P. catalpifolia. Moreover, we observed leaf wilting symptoms distinctly after exposure to ELT for 48 h, while this effect was not obvious after MLT exposure for 48 h. Comparative transcriptomic analysis between MLT and ELT demonstrated 13,688 differentially expressed genes (DEGs), most of them appeared after 12 h and 48 h of treatment. GO and KEGG analyses elucidated prominent enrichment in aromatic-L-amino-acid decarboxylase activity term and carbohydrate metabolism pathways. Therefore, it was speculated that the DEGs involved in the above processes might be related to the difference in the contents of soluble protein and soluble sugar between MLT and ELT. Time series clustering analyses further highlighted several key genes engaged in the 'Glycosyltransferases', 'Galactose metabolism' and 'Starch and sucrose metabolism' pathways as well as the 'tyrosine decarboxylase activity' term. For instance, cellulose synthase-like A (CLSA2/9), raffinose synthase (RafS2), ß-amylase (BAM1) and tyrosine/DOPA decarboxylase (TYDC1/2/5) genes, diverging in their expression trends between MLT and ELT, might significantly affect the soluble sugar and soluble protein abundance within P. catalpifolia. CONCLUSION: Between MLT and ELT treatments, partial overlaps in response pathways of P. catalpifolia were identified, while several genes regulating the accumulation of osmotic adjustment substances had disparate expression patterns. These findings could provide a novel physiological and molecular perspective for P. catalpifolia to adapt to complex low temperature habitats.

[Research on optimization system on tissue culture and rapid propagation of Pueraria mirifica].

OBJECTIVE: To study the tissue culture and rapid-proliferation techniques of Pueraria mirifica. METHOD: The tender branch were used as explants and cultivated in different media. The optimum media for inducing buds, proliferation and rooting were selected by adjusting the kinds and doses of plant hormones and special compounds. RESULT: The medium of MS + IBA 0.05 mg L(-1) + BA 0.5 mg L(-1) was suitable for buds inducing and could be used in the first generation cultivation; MS + IBA 0. 02 mg L(-1) + BA 0.2 mg L(-1) and MS +BA 0.1 mg L(-1) were employed by turns in subculture, 25 days propagation coefficient was 3.0; and the medium of 1/2MS + IBA 0.1 mg L(-1) + IAA 0.2 mg L(-1) + C (special compound) 10 mg L(-1) was used for roots inducing, the rooting rate was 76.9%. Rooting plantlets were transplanted in spring and summer; the surviving rate was 81.0%. CONCLUSION: This technique system could be employed for rapid propagation of P. mirifica.