Navigation Links
Plant's immune defense revs up for the morning attack
Date:2/3/2011

DURHAM, N.C. Timing is everything in the long-standing arms race between the flowering plant Arabidopsis and Hyaloperonospora, a downy mildew pathogen.

Duke University researchers have found that the little mustard plant cranks up its immune system in the morning to prepare for the greatest onslaught of infectious spores released by the mildew.

It isn't news that plants know what time of day it is and change their activities accordingly, but this is the first time that a plant's defensive systems have been shown to cycle on a daily basis even when pathogens aren't present. Their work appears in the Feb. 3 edition of Nature.

The powerful chemical compounds Arabidopsis uses to fight mildew infection are expensive to make and also potentially harmful to the plant itself over the long-term, so a daily, or circadian, cycle of production is safer and more efficient than simply having the chemicals on hand all the time, said Duke biology professor Xinnian Dong.

Morning, just as the dew dries, is the right time to have defenses at the ready.

When the mildew has been able to successfully set up housekeeping within Arabidopsis, it produces a flowering body that grows upward from the leaf surface. Bearing its spores for the next generation, it looks very much like a tree covered with apples. As the morning dew dries from the leaf, the mildew's flowering body twists violently, flinging the tiny spores in all directions to be carried on air currents until they settle on a potential new host.

Other researchers who have collected the spores had noted that the morning was the most productive time to catch them, but Arabidopsis apparently already knew that.

Dong and her graduate students Wei Wang and Jinyoung Barnaby discovered this surprising circadian clock connection during a more general search of Arabidopsis immune system genes. They found 22 candidate genes that were a part of the immune response to downy mildew and many of them showed rhythmic expression patterns.

Wang also watched expression patterns of these defense genes in the absence of any pathogens and found them cycling daily. "It suggests that the plants are programmed to anticipate infection according to a circadian schedule," Dong said.

To test this hypothesis, Wang exposed plants to the mildew spores at "dawn" or "dusk" in a greenhouse with artificial 12-hour days. He found infection rates were much higher at dusk when spores were not expected in nature.

To identify the clock components that control this immune defense, Wang began a series of experiments on so-called "clock mutants," which are Arabidopsis plants that lack portions of the circadian time-keeping system. He found that the mutant missing the central clock component CCA1 suffered much higher infection rates than normal plants. Conversely, a plant line expressing CCA1 all the time had heightened resistance.

Over the last decade, plant researchers have identified several systems that work on a circadian clock, including starch metabolism, photosynthesis and frost-resistance, said Robert McClung, a Dartmouth University biologist who was not involved in this research, but is writing an accompanying commentary on the paper for Nature. "This sort of completes the suite of environmental insults that the clock manages," he said.

Although this finding is specific so far to Arabadopsis and its exclusive pathogen Hyaloperonospora, it's likely to be a system that will be found in other plants and pathogens, McClung said.

While it makes logical sense that clock mechanisms would be involved with the plant's immune system, this is still "a remarkable discovery," said Philip Benfey, the Paul Kramer professor of biology at Duke. "This required an experimental tour de force combined with inspired insight to make the connection between gene expression patterns and preparation for pathogen attack."

"It was a huge amount of work, even though the conclusion is quite simple," Dong said.


'/>"/>

Contact: Karl Leif Bates
karl.bates@duke.edu
919-681-8054
Duke University
Source:Eurekalert

Related biology news :

1. Commercial aquatic plants offer cost-effective method for treating wastewater
2. UC Riverside biochemists devise method for bypassing aluminum toxicity effects in plants
3. Reproducing early and often is the key to rapid evolution in plants
4. MSU scientists find new gene that helps plants beat the heat
5. Researchers design artificial cells that could power medical implants
6. When under attack, plants can signal microbial friends for help
7. Current mass extinction spurs major study of which plants to save
8. Scientists unveil mechanism for up and down in plants
9. New hybrid plants could prompt more prodigious pepper production in Southwest
10. Extreme weather postpones the flowering time of plants
11. Even plants benefit from outsourcing
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/28/2016)... and BANGALORE, India , April ... EdgeVerve Systems, a product subsidiary of Infosys (NYSE: ... today announced a global partnership that will provide ... to use mobile banking and payment services.      ... a key innovation area for financial services, but it also ...
(Date:4/26/2016)... and LONDON , ... Finacle, part of EdgeVerve Systems, a product subsidiary ... Onegini today announced a partnership to integrate the ...      (Logo: http://photos.prnewswire.com/prnh/20151104/283829LOGO ) ... provide their customers enhanced security to access and ...
(Date:4/19/2016)... DUBAI , UAE, April 20, 2016 ... can be implemented as a compact web-based "all-in-one" system ... in the biometric fingerprint reader or the door interface ... requirements of modern access control systems. The minimal dimensions ... the ID readers into the building installations offer considerable ...
Breaking Biology News(10 mins):
(Date:5/3/2016)... 2016 - And Other Rising ... of Those Competitor Biologics  - Biosimilar Drug ... Prospects ,  Who are the most important ... are their sales potentials? Discover, in our updated survey, ... opportunities and revenue forecasting. Visiongain,s ...
(Date:5/3/2016)... ... 03, 2016 , ... Nashville Fertility Center has joined a ... reproductive endocrinologists, including Dr. George Hill at Nashville Fertility Center, created ... build families. , Ovation Fertility is a nationwide network of leading fertility centers ...
(Date:5/2/2016)... ... May 02, 2016 , ... StarNet Communications Corp, ( ... the addition of three Secure Remote Desktop modules to its flagship X-Win32 PC X ... Linux and Unix servers to the user’s PC over encrypted SSH. , Traditionally, users ...
(Date:4/29/2016)... ... 2016 , ... Proove Biosciences, Inc ., the commercial ... of the Proove Health Foundation . The Foundation is a non-profit organization ... of personalized medicine for tackling the nation’s most-pressing healthcare epidemics. As part of ...
Breaking Biology Technology: