Ethylene augments root hypoxia tolerance via growth cessation and reactive oxygen species amelioration

Flooded plants experience impaired gas diffusion underwater, leading to oxygen deprivation (hypoxia). The volatile plant hormone ethylene is rapidly trapped in submerged plant cells and is instrumental for enhanced hypoxia acclimation. However, the precise mechanisms underpinning ethylene-enhanced hypoxia survival remain unclear. We studied the effect of ethylene pre-treatment on hypoxia survival of Arabidopsis (Arabidopsis thaliana) primary root tips. Both hypoxia itself and re-oxygenation following hypoxia are highly damaging to root tip cells, and ethylene pre-treatments reduced this damage. Ethylene pre-treatment alone altered the abundance of transcripts and proteins involved in hypoxia responses, root growth, translation, and reactive oxygen species (ROS) homeostasis. Through imaging and manipulating ROS abundance in planta, we demonstrated that ethylene limited excessive ROS formation during hypoxia and subsequent re-oxygenation and improved oxidative stress survival in a PHYTOGLOBIN1-dependent manner. In addition, we showed that root growth cessation via ethylene and auxin occurred rapidly and that this quiescence behavior contributed to enhanced hypoxia tolerance. Collectively, our results show that the early flooding signal ethylene modulates a variety of processes that all contribute to hypoxia survival

Behavioural Impact of Enclosure Relocation on Asiatic Elephants (Elephas maximus) in Artis Royal Zoo, Amsterdam

It can have negative consequences when the standards of well-being of animal are not met in a captive environment. The main priority of this study was to determine whether a more enriched enclosure could reduce stereotypic behaviour and increase natural behaviours in captive Asiatic elephants, and thus increase well-being. In order to answer this question the Asiatic elephants in Artis Royal Zoo were studied. Artis Royal Zoo had built a new enclosure to improve the well-being of their elephants. Activity budgets of the three elephants of both the new and old enclosure were studied. Observation was done over a period of three months ,between April 2017 and July 2017 for a total of 26 days. Only Thong-Thai, mother of Yindee and Sanuk, exhibited stereotypic behaviour. There was a significant difference found between the stereotypic behaviour averages per enclosure when consume/forage behaviour and enclosures were included in the model. Both Thong-Thai and Yindee reduced their consume/foraging behaviour when relocated. All three elephants increased in walking behaviour when relocated with a maximum difference exhibited by Yindee. Only Yindee increased in enrichment use behaviour. Also, like Rees (2009), a negative correlation was found between stereotypic behaviour and consume/foraging behaviour in both enclosures. The behavioural data can only give an indication of improved well-being and we may not have seen extreme positive signs yet but we can say that the new enclosure provides a more abundant set of options to the elephants. These extra options remove mental and physical barriers and stimulate the animal to exhibit natural behaviour which can only be a good thing (McPhee & Carlstead, 2010)

Ethylene augments root hypoxia tolerance via growth cessation and reactive oxygen species amelioration

Flooded plants experience impaired gas diffusion underwater, leading to oxygen deprivation (hypoxia). The volatile plant hormone ethylene is rapidly trapped in submerged plant cells and is instrumental for enhanced hypoxia acclimation. However, the precise mechanisms underpinning ethylene-enhanced hypoxia survival remain unclear. We studied the effect of ethylene pre-treatment on hypoxia survival of Arabidopsis (Arabidopsis thaliana) primary root tips. Both hypoxia itself and re-oxygenation following hypoxia are highly damaging to root tip cells, and ethylene pre-treatments reduced this damage. Ethylene pre-treatment alone altered the abundance of transcripts and proteins involved in hypoxia responses, root growth, translation, and reactive oxygen species (ROS) homeostasis. Through imaging and manipulating ROS abundance in planta, we demonstrated that ethylene limited excessive ROS formation during hypoxia and subsequent re-oxygenation and improved oxidative stress survival in a PHYTOGLOBIN1-dependent manner. In addition, we showed that root growth cessation via ethylene and auxin occurred rapidly and that this quiescence behavior contributed to enhanced hypoxia tolerance. Collectively, our results show that the early flooding signal ethylene modulates a variety of processes that all contribute to hypoxia survival