Hydrogen peroxide is involved in drought stress long-distance signaling controlling early stomatal closure in tomato plants.

It has long been hypothesized that hydrogen peroxide (H2O2) may play an essential role in root-to-shoot long-distance signaling during drought conditions. Thus, to better understand the involvement of H2O2 in drought signaling, two experiments were carried out using tomato plants. In the first experiment, a split-root scheme was used, while in the second experiment, the tomato plants were grown in a single pot and subjected to drought stress. In both experiments, H2O2 and catalase were applied together with irrigation. Control plants continued to be irrigated according to the water loss. In the split-root experiment, it was verified that the application of H2O2 to roots induced a clear reduction in plant transpiration compared to untreated or catalase-treated plants. In the second experiment, we observed that H2O2-treated plants exhibited similar transpiration when compared to untreated and catalase-treated plants under drought stress. Similarly, no difference in water use efficiency was observed. Thus, we conclude that the increase in H2O2 in the root system can act as a long-distance signal leading to reduced transpiration even when there is no water limitation in the shoot. But it has little effect when there is a reduction in the shoot water potential.

Hydrogen peroxide is involved in drought stress long-distance signaling controlling early stomatal closure in tomato plants / O peróxido de hidrogênio está envolvido na sinalização de longa distância do déficit hídrico controlando o fechamento estomático precoce em plantas de tomate

It has long been hypothesized that hydrogen peroxide (H2O2) may play an essential role in root-to-shoot long-distance signaling during drought conditions. Thus, to better understand the involvement of H2O2 in drought signaling, two experiments were carried out using tomato plants. In the first experiment, a split-root scheme was used, while in the second experiment, the tomato plants were grown in a single pot and subjected to drought stress. In both experiments, H2O2 and catalase were applied together with irrigation. Control plants continued to be irrigated according to the water loss. In the split-root experiment, it was verified that the application of H2O2 to roots induced a clear reduction in plant transpiration compared to untreated or catalase-treated plants. In the second experiment, we observed that H2O2-treated plants exhibited similar transpiration when compared to untreated and catalase-treated plants under drought stress. Similarly, no difference in water use efficiency was observed. Thus, we conclude that the increase in H2O2 in the root system can act as a long-distance signal leading to reduced transpiration even when there is no water limitation in the shoot. But it has little effect when there is a reduction in the shoot water potential.

Tem sido hipotetizado que o peróxido de hidrogênio (H2O2) pode desempenhar um papel essencial na sinalização de longa distância entre a raiz e a parte aérea sob condições de seca. Assim, para melhor entender o envolvimento do H2O2 na sinalização da seca, dois experimentos foram realizados com plantas de tomate. No primeiro, foi utilizado o esquema de raízes divididas, enquanto no segundo, os tomateiros foram cultivados em um único vaso e submetidos ao déficit hídrico. Em ambos os experimentos, o H2O2 e a catalase foram aplicados juntamente com a irrigação. As plantas do grupo controle continuaram a ser irrigadas de acordo com a perda de água. No experimento de raiz dividida, verificou-se que a aplicação de H2O2 nas raízes induziu uma clara redução na transpiração da planta em comparação com plantas não tratadas ou tratadas com catalase. No segundo experimento, observamos que plantas tratadas com H2O2 apresentaram transpiração semelhante quando comparadas com plantas não tratadas e tratadas com catalase sob seca. Da mesma forma, não foi observada diferença na eficiência do uso da água. Assim, concluímos que o aumento do H2O2 no sistema radicular pode atuar como um sinal de longa distância levando à redução da transpiração mesmo quando não há limitação hídrica na parte aérea. Mas tem pouco efeito quando há redução do potencial hídrico da parte aérea.

In vivo 5-fluorouracil-[corrected]induced apoptosis on murine thymocytes: involvement of FAS, Bax and Caspase3.

Apoptosis is a highly regulated and programmed cell breakdown process characterized by numerous changes. It was reported as the major mechanism of anticancer drug-induced cells death. Unfortunately, many of these drugs are non-specific and cause severe side effects. The effects of 5-fluorouracil (5-FU) on the apoptotic events in normal murine thymus were evaluated using an in vivo model. A single dose of 5-FU (150 mg/kg ip) was injected to CF-1 mice. A multiparametric analysis of thymic weight, cellularity, viability, architectural organization, apoptosis, DNA fragmentation, and the expression of several apoptotic proteins was evaluated in 10 days time-course study post-5-FU dosing. Total organ weights, thymocyte counts, and cell viabilities diminished drastically from the second day. The thymus architecture assessed through electron scanning microscopy revealed deep alterations and the lost of cell-cell contact between the first and the third days. DNA fragmentation and apoptotic indexes (May Grünwald Giemsa staining, double fluorescent dyes, and TdT-mediated dUTP nick-end labeling assay) revealed that cell death was maximal on the second day (three times over control). Furthermore, the pro-apoptotic proteins FAS and Bax were strongly up-regulated during the first 2 days. The aforementioned morphological and biochemical changes were also accompanied within the same period by caspase 3 activation. This study revealed that in vivo apoptosis in normal thymus after 5-FU administration is related to FAS, Bax, and Caspase 3 co-expressions under the current experimental conditions, these findings, therefore, contribute to a new insight into the molecular mechanisms involved during 5-FU administration upon the thymus and the possible events committed in the lymphophenia associated with chemotherapy.