JXB Advance Access originally published online on February 4, 2008
Journal of Experimental Botany 2008 59(3):521-532; doi:10.1093/jxb/erm326
Focus Review Paper |
From plants to animals; the role of plant cell death in ruminant herbivores
Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth SY23 3EB, UK
* To whom correspondence should be addressed. E-mail: alison.kingston-smith{at}bbsrc.ac.uk
Plant cell death occurring as a result of adverse environmental conditions is known to limit crop production. It is less well recognized that plant cell death processes can also contribute to the poor environmental footprint of ruminant livestock production. Although the forage cells ingested by grazing ruminant herbivores will ultimately die, the lack of oxygen, elevated temperature, and challenge by microflora experienced in the rumen induce regulated plant stress responses resulting in DNA fragmentation and autolytic protein breakdown during the cell death process. Excessive ruminal proteolysis contributes to the inefficient conversion of plant to microbial and animal protein which results in up to 70% of the ingested nitrogen being returned to the land as the nitrogenous pollutants ammonia and urea. This constitutes a significant challenge for sustainable livestock production. As it is estimated that 25% of cultivated land worldwide is assigned to livestock production, it is clear that understanding the fundamental biology underlying cell death in ingested forage will have a highly significant role in minimizing the impact of human activities. This review examines our current understanding of plant metabolism in the rumen and explores opportunities for exploitation of plant genetics to advance sustainable land use.
Key words: Anoxia, cell death, environment, heat, plant–microbe interactions, proteolysis
Received 7 September 2007; Revised 21 November 2007 Accepted 23 November 2007