When a heat wave sent tomato prices soaring this past summer, before the High Holidays, Israelis got a taste of the precarious nature of our food supply: Any climate upheaval can instantly create dire shortages of food staples. Even in the absence of natural disasters, securing the world’s food supply in the 21st century promises to be a tall order: Global population continues to grow while the areas of cultivated land tend to remain stable – a situation that is bound to lead to food shortages, and will be further aggravated by global warming.
“It’s vitally important to keep up the green revolution,” says Prof. Robert Fluhr
, referring to the increases in yields that in the second half of the 20th
century saved much of the world from starvation. “Adapting agriculture to meeting the world’s needs is a continuous battle. We must stay on our toes in order to win.”
Feeding the world is all the more challenging because a staggering proportion of crop yields worldwide – above 30 percent – is regularly lost to pests, disease and weather. Prof. Fluhr’s laboratory in the Weizmann Institute’s Plant Sciences Department focuses on research that can help increase yields by reducing these losses. In particular, the lab’s research is aimed at understanding – and ultimately enhancing – the plant’s natural defenses against a variety of ills.
In a recent collaborative study with researchers from Australia, Fluhr’s team has taken an important step in this direction. The scientists have unraveled the control switch for a crucial plant growth- and survival- mechanism: the killing of individual plant cells by activating enzymes called proteases that chop up essential proteins. These enzymes come into play when the plant is trying to control the spread of a disease or needs to recover nutrients from old unused leaves. It’s crucially important, however, that the proteases work at precisely the pace needed to ensure the plant’s survival: fast enough to contain a disease, for example, but not so fast as to cause this rescue operation to kill the entire plant.
The new study led by Prof. Fluhr
has defined a potential “pace-setter” that can determine the rate at which proteases perform their “constructive destruction”: a molecule belonging to the family of proteins called serpins. The molecule, referred to as AtSerpin1, functions like a molecular mousetrap, latching onto a specific protease and inactivating it when the destruction must be slowed down. In this manner, AtSerpin1 determines the pace at which cell death will occur in the plant. The study, published in the Journal of Biological Chemistry
, was performed by former graduate student Dr. Nardy Lampl, and Drs. Ofra Budai-Hadrian and Olga Davydov of the Weizmann Institute’s Plant Sciences Department, in collaboration with Australian researchers: Tom V. Joss and Dr. Thomas H. Roberts of Macquarie University and Dr. Stephen J. Harrop and Prof. Paul M. G. Curmi of the University of New South Wales, in Sydney.
The serpin “pace-setter” must be an unusually effective mechanism, for it has been in use for at least a billion years – a sure sign of evolutionary success. In fact, it exists both in plants and in animals and can be traced back to their common ancestors, single-celled eukaryotes (that is, cells possessing a nucleus) that in Earth’s distant past gave rise to plant and animal kingdoms alike. In mammals, including humans, serpin-controlled proteases perform a variety of functions in immunity, blood clotting and development.
The fact that in animals many protease activities are regulated by serpins has been known for a number of years, but the Weizmann Institute-led study represents the first time the serpin “pace-setter” and the specific protease with which it interacts have been identified in plants. The study was performed on Arabidopsis, a convenient model plant related to mustard; but genome analysis suggests that the findings are applicable to the entire plant kingdom. These findings open up a new avenue of research that can identify additional “pace-setters,” that is, other serpin molecules regulating the activity of different proteases. The ultimate goal: an in-depth understanding of plant defenses that can help create hardier plants, minimizing loss in the face of adversity.
Fluhr says that achieving this goal has a special urgency: “As a country where overcrowding, water shortage and the scarcity of arable land make agriculture particularly vulnerable to environmental impact, Israel can set an example for increasing crop productivity worldwide.”
Prof. Robert Fluhr's research is supported by Joel Jacob, Bloomfield, MI. Prof. Fluhr is the incumbent of the Sir Siegmund Warburg Professorial Chair of Agricultural Molecular Biology.