martes, 13 de marzo de 2018

How do plants sense stress and activate survival?

Scientists from the University of Nottingham recently announced more advancements on the current knowledge about how plants sense environmental stress.

Vicente et al. (2017), published in the journal Current Biology in October 2017, used data on Arabidopsis and barley to illustrate how plants make use of a protein degradation pathway to sense multiple environmental stresses such as high salinity, drought, and high temperature.

This pathway, named the N-end rule pathway, was initially described as the mechanism plants use to sense environmental clues such as the level of oxygen (O2) (Gibbs et al., 2011) and nitric oxide (NO) (Gibbs et al., 2014) that characterise a wide range of environmental stresses. For example, flooding is associated with low levels of oxygen in the soil. The dynamics of this sensing mechanism are such that under normal levels of O2 and NO, specific proteins are oxidised and targeted for degradation in the cell. However, under low O2 (flooding) or low NO, the same proteins do not get degraded and are stabilised in the cell, instead. These proteins are then expected to change the expression of many genes associated with stress tolerance and survival.

Prof. Michael Holdsworth, Dr Jorge Vicente and Dr Guilhermina Mendiondo showed that the interruption of the pathway led to enhanced plant resilience to a range of environmental stresses (high salinity, drought, and high temperature) in Arabidopsis and barley plants.

Furthermore, the scientists investigated which environmental clue (O2 or NO) was actively being sensed by the plant during specific types of environmental stress. They were able to verify that high salinity caused a large decline in the enzyme nitrate reductase, which in turn reduced the level of NO, placing NO sensing in the centre of the plant response to this environmental stress.

Additionally, the researchers also investigated how stress-led protein stabilisation in the plant cell resulted in increased tolerance to stress. Upon stress exposure, they were able to observe an interaction between the stabilised proteins and the protein BRAHMA, which is involved in chromosome folding and thus modulates the access of gene expression regulatory proteins to the DNA. This result adds to the current understanding of how environmental sensing through the N-end rule pathway subsequently leads to enhanced stress tolerance and the activation of survival mechanisms.

The understanding of the molecular mechanisms used by plants to tolerate and survive environmental stresses might help plant breeders to generate crop varieties more capable of providing stable yields and higher quality harvests under environmentally challenging conditions. This study is particularly relevant in a world evermore affected by extreme weather events and climate change.