Effect of Artificial Light Conditions on Local and Systemic Resistance Response of Tobacco to TMV Infection

Abstract

Our and literature studies indicated that systemic acquired resistance (SAR) is effectively inducible in greenhouse, and certain artificial light sources cause non-optimal growth of tobacco plants. Therefore, the morphological characteristics, local and systemic resistance response of N. tabacum cv. 'Xanthi' nc plants (harbouring NN resistance genes) to tobacco mosaic virus (TMV) infection under three artificial light sources with different spectral distribution were compared with greenhouse conditions. Statistical analysis of data was carried out by R package (R Core Team, 2015). Generally, artificial light sources (especially fluorescent tube and halogen lamp) decreased the local resistance response and caused substantial morphological and developmental differences as compared to greenhouse conditions when plants were kept during their entire life (lifelong experimental regime) under these conditions. On the contrary, no or much less differences were found when plants were transferred from greenhouse to artificial light sources only at six leaf stage (short experimental regime). While induction of SAR frequently decreased TMV lesion size by about 50-60% under greenhouse conditions, two of the three artificial light sources, fluorescent tube and halogen lamp were substantially and significantly less effective under short experimental regime conditions (25-35%). A metal halide light source with similarity to sunshine's spectral distribution, however, partially mimicked the effect of greenhouse conditions indicating the importance of light spectrum among other factors in SAR induction and prevention of distorted growth of plants. Consequently, the optimization of the effect of artificial light sources is an important factor in experimental design studying signal transduction and biochemistry of SAR.

Signals of Systemic Immunity in Plants: Progress and Open Questions

“…The systemic FMO1 and PR1 expression and SA level were not inducible as well as SAR could not develop in the double mutant phyA - phyB plants. It is possible that the phytochrome mediated effect is related to the effect of spectral distribution of light on SAR [ 32 ].…”

“…The third light-dependent factor that can cause differences in resistance to TMV infection is the spectral distribution of light [ 32 ]. Our results clearly indicated that spectral distribution of light sources influences (i) plant growth and development; (ii) local resistance response to TMV infection and (iii) SAR inducing capacity of tobacco plants.…”

“…From a practical point of view, under artificial conditions, metal halide lamp or a mixture of HL and FT light sources can be suggested as optimal test conditions. Consequently, the optimization of the effect of artificial light sources is an important factor in experimental design studying signal transduction and biochemistry of SAR [ 32 ].…”

“… Effect of local (CL and L2) and systemic (CS, S2 and S10) pipecolic acid ( d - l -Pip) treatments on TMV lesion size distribution by using Kernel density estimation [ 31 , 32 ] (2 days after Pip infiltration). L2, S2 and S10: local (L, leaf 6) and systemic (S, leaf 7) effects of 2 and 10 mM d - l -Pip treatments as compared to corresponding local control (CL) and systemic control (CS) leaves (triplicate per treatments).…”

“…However, considering recent data about multiple signal mechanisms with diverse chemical substances described mainly in Arabidopsis -bacteria plant-pathogen systems it is reasonable to test whether this multiple signalling is due to environmental or some other circumstantial factors. It is especially true for tobacco where less experimental data is available and a virus-inducible SAR response could be also studied by using a computer-assisted method for symptoms evaluation and statistical analysis [ 28 , 30 , 31 , 32 ].…”