The Role Of RBOH1in The BR-Promoted Photosynthesis And The Effect Of MAPK1/2in Response To Wound And Different Light Qualities In Tomato

Tomato(Solarium lycopersicum) is one of the major vegetables cultivated worldwide for its high nutritional value, market price and productivity. Tomato is also considered as a model plant material in horticultural research. In the current study, we silenced RBOH1in the commercial cultivar of tomato Hezuo903using VIGS (virus induced gene silencing) approach. The resulting pTRV and pTRV-RBOH1were used for the following experiments.1. The role of RBOH1in the BR-promoted photosynthesisIn this experiment, pTRV and pTRV-RBOH1plants were sprayed either with0.2μM EBR or ddH2O (control). We recorded the photosynthesis-related parameters and PSII-related parameters of pTRV and pTKV-RBOH1under different treatments. The relative expression of TRXs and2-CPs was also quantified.We found that the gas exchange parameters such as Pn, Gs, Ci and Tr were significantly increased in pTRV3h after EBR treatment compared to its control. However, Gs of pTRV showed no difference12h after EBR treatment with the control, while prominent difference in Pn still existed. The four parameters showed no significant rise in pTKV-RBOH13h or6h after EBR treatment compared to its control, but presented a similar result as that in pTRV12h after treatment. We assume that shortly after EBR treatment (3h), low concentration of EBR can promote the stomatal opening which induces transpiration rate and gas exchange, and thereby increasing net photosynthesis. Investigation on photosystem Ⅱ showed that Y(Ⅱ) was decreased, but Y(NPQ) was increased at night, while EBR made no difference.The transcripts of TRXs and2-CPs in pTRV, remained unaltered6h after EBR treatment, whereas significant difference appeared12h after treatment. We suppose that at the later period of EBR treatment (12h), EBR promotes some photosynthesis-related genes, including TRXs and2-CPs, which then activate some important photosynthesis-related enzymes and eventually improve photosynthesis.2. The activation on MAPK1/2by different light qualities We applied different light qualities on pTRV, pTRV-RBOH1and phytochrome mutants, then recorded Gs and sampled to quantify activity of MAPK1/2. The induction on MAPK1/2by different light qualities seems quite different. For example, MAPK1/2in pTRV decreased after lmin red light treatment but increased afterward. Far-red light showed the opposite effect of red light.White light, red light and blue light each had the effect on stomatal opening. Although far-red light could not induce stomatal opening, it enhanced the effect of red light. When RBOH1was silenced, effect of red light on stomatal opening disappeared, while blue light could still regulate stomatal opening, but the effect was not so strong as that in pTRV. These results suggest that blue-light response in stomatal opening is independent of H2O2, while the photosynthesis-prompted stomatal opening by either red light or blue light is H2O2-dependent.3. The wound-induced MAPK1/2We applied wound on some areas of the leaf and then sampled to quantify MAPK1/2activity.MAPK1/2was obviously induced10min after wounding (puncture) in the very leaflet. The opposite leaflet of the wounded one showed a tremendous induction of MAPK1/230min after treatment. Parallel tests on pTRV and pTRV-RBOH1both showed the similar tendency. Comparing pTRV and pTRV-RBOH1, we found that the expression of MAPK1/2was stronger in the latter one.