G. Inei-Shizukawa, H. A. Velasco-Bedrán, G. F. Gutiérrez-López and H. Hernández-Sánchez Abstract Castilleja tenuiflora Benth, is a medicinal plant that synthesizes secondary metabolites such as phenylethanoid glycosides (PhGs), flavonoids, lignans, and iridoid glycosides with pharmacological properties. Nutrient deficiency stress in in vitro culturing of plants has been shown to be a good biotechnological strategy to stimulate secondary metabolism. Our aim was to evaluate morphogenesis (growth and development) and the production of secondary metabolites in C. tenuiflora shoots in response to stress by nitrogen (N) deficiency and starvation in temporary immersion bioreactors. Shoots were grown in B5 liquid medium with 25.74 mM (control), 1.32, 0.66 (deficiency) and 0 mM (starvation) N concentration. In all treatments, matter and shoot multiplication rate (SMR) decreased over 40%, chlorophylls content decreased, roots length increased, and leaves showed chlorosis respect to control. Under 0.66 mM N deficiency, the enzyme phenylalanine ammonia lyase (PAL) was more active (twice more than control) and total phenolic compounds were enhanced. At day 21: maximum concentration of PhGs (verbascoside and isoverbascoside) and iridoids (aucubin) was observed in 0.66, 1.32 and 0 mM N treatments (283 ± 0.5, 90 ± 0.3 and 12.5 ± 0.1 mg g −1 DM, respectively); these concentrations were 175, 143 and 34% greater than respective controls on the same day. Additionally, presence of anthocyanins was evident in stems of all plants developed under N deficiency and starvation. Despite the fact that, the matter, SMR and chlorophylls decreased because N stress deficiency, the production of secondary metabolites was enhanced, demonstrating that in vitro culture in temporary immersion bioreactors under suitable nutrients deficit such as N is an appropriate strategy to stimulate secondary metabolism in C. tenuiflora. Keywords: abiotic stress, Aucubin, nitrogen starvation, phenylethanoid glycosides, RITA® bioreactor.
ResumenCastilleja tenuiflora Benth., es una planta medicinal que sintetiza metabolitos secundarios como feniletanoides glicosilados (PhGs), flavonoides, lignanos, e iridoides; que presentan actividad farmacológica. El estrés por deficiencia de nutrientes en el cultivo de plantas in vitro ha mostrado ser una estrategia biotecnológica apropiada para estimular su metabolismo secundario. En este trabajo se evaluaron la morfogénesis (crecimiento y desarrollo) y la producción de metabolitos secundarios en brotes de C. tenuiflora en biorreactores de inmersión temporal expuestos a estrés por deficiencia y ausencia de nitrógeno (N). El estrés se aplicó a un cultivo de los brotes cultivados en medio líquido B5 con 25.74 mM (control), 1.32, 0.66 (deficiencia) y 0 mM (ausencia) de N. En comparación con el control, todos los tratamientos mostraron una disminución de más del 40% en la biomasa y elíndice de multiplicación de brotes, el contenido de clorofila disminuyó, la longitud de las raíces aumentó y las hojas mostraron clorosis. En defi...