MSGID: 1:317/3 627201de   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    In poplars, two plant hormones boost each other in defense against   
   pathogenic fungi    
      
     Date:   
         May 3, 2022   
     Source:   
         Max Planck Institute for Chemical Ecology   
     Summary:   
         In contrast to previous assumptions, the defense hormones   
         salicylic acid and jasmonic acid do not always suppress each   
         other in regulating plant chemical defenses against pests and   
         pathogens. In trees, the interplay of both hormones can actually   
         increase plant resistance.   
      
      
      
   FULL STORY   
   ==========================================================================   
   In contrast to previous assumptions, the defense hormones salicylic acid   
   and jasmonic acid do not always suppress each other in regulating plant   
   chemical defenses against pests and pathogens. In trees, the interplay   
   of both hormones can actually increase plant resistance. This is the   
   conclusion researchers from the Max Planck Institute for Chemical Ecology   
   draw in a new study on poplars.   
      
   The scientists showed that higher levels of jasmonic acid were also   
   detectable in poplars that had been modified to produce increased levels   
   of salicylic acid or that had been treated with salicylic acid. Plants   
   that had higher concentrations of both hormones were also more resistant   
   to the rust fungus Melamspora larici-populina, with no negative effect on   
   growth. Knowledge of the positive interaction of these hormones involved   
   in plant resistance could help to better protect poplars and other trees   
   against pathogens.   
      
      
   ==========================================================================   
   The function of plant hormones or phytohormones is to coordinate the   
   growth and development of plants. Moreover, they also control plant immune   
   responses to microbial pathogens such as pathogenic fungi. Until now,   
   there has been a broad consensus in science that the signaling pathways   
   of the defense hormones salicylic acid and jasmonic acid act in opposite   
   directions. Thus, if plants produce more salicylic acid, this would   
   inhibit the production of jasmonic acidand vice versa. Scientists have   
   repeatedly shown this negative interplay in studies of the model plant   
   Arabidopsis thaliana (thale cress) and many other annual herbs. "Contrary   
   to the assumption that the salicylic acid and jasmonic acid hormone   
   signaling pathways work in an opposite manner, we had already observed   
   in our earlier studies on poplar trees that both of these hormones   
   increase in response to infection by pathogenic fungi. Therefore, the   
   main research question was to determine the interaction between these   
   two defense hormones in poplar," Chhana Ullah, first author of the   
   publication, explains the starting point of the current study.   
      
   To study experimentally how salicylic acid levels affect the formation   
   of jasmonic acid, the scientists genetically modified experimental   
   plants of black poplar (Populus nigra) native to Germany so that they   
   produced higher amounts of salicylic acid than control plants. In   
   another experiment, they applied salicylic acid to the poplar leaves of   
   genetically unmodified plants. "We manipulated salicylic acid levels in   
   poplar by genetic engineering and direct chemical application, after   
   which we conducted extensive chemical analyses of the plants with and   
   without fungal infection. This allowed us to separate the effects of   
   salicylic acid from other factors and show that it directly stimulates   
   jasmonic acid production," explains Chhana Ullah.   
      
   Plants that contained high levels of salicylic acid also had higher   
   concentrations of jasmonic acid. In addition, these plants produced   
   more antimicrobial substances, known as flavonoids, even if there was   
   no infection with a pathogen. Further comparative studies with plants   
   that produced high levels of salicylic acid and control plants that   
   had each been infected with the rust fungus Melamspora larici-populina   
   showed that high levels of salicylic acid made poplars more resistant   
   to fungal attack.   
      
   Surprisingly, higher fungal resistance due to increased defenses did not   
   negatively affect plant growth, as had been observed in Arabidopsis and   
   other annual herbs. In Arabidopsis, either salicylic acid or jasmonic   
   acid takes control of the immune response, while the other hormone   
   is suppressed.   
      
   Salicylic acid is produced in higher amounts after attack by biotrophic   
   pathogens that do not kill plant tissue and feed on living plant material,   
   while jasmonic acid is increased after attack by insects or necrotrophic   
   pathogens that feed on dead plant tissue. "The negative interplay between   
   the defense hormones salicylic acid and jasmonic acid in plants like   
   Arabidopsis enables the plant to prioritize protection against one kind   
   of enemy. Small herbs like Arabidopsis may benefit from such a narrow   
   focus because they lack the resources to defend against different kinds of   
   enemies at once. This may also be the reason why Arabidopsis plants reduce   
   their growth rate when in a defense mode," says Jonathan Gershenzon,   
   head of the Department of Biochemistry where the study was conducted.   
      
   In contrast to annual herbs such as thale cress, resources are usually   
   less limited for trees and other woody plants. Moreover, because of   
   their long lifespan, trees are often attacked simultaneously by different   
   enemies, such as fungal and bacterial pathogens, leaf-eating caterpillars,   
   and wood-destroying insects. They may have evolved to use the salicylic   
   and jasmonic acid signaling pathways together for defense. The greater   
   availability of resources in long- living woody plants may also be the   
   reason why high concentrations of salicylic acid do not affect plant   
   growth in poplars.   
      
   The researchers were surprised to find that high levels of salicylic   
   acid in poplars did not activate so-called pathogenesis-related (PR)   
   genes, although these are established markers for the salicylic acid   
   signaling pathway in Arabidopsis. "However, we found that the magnitude   
   of PR gene induction was positively correlated with the susceptibility   
   of poplar to rust. Apparently, the activation of PR genes in poplar is   
   not regulated by salicylic acid signaling, but by a different mechanism,"   
   Chhana Ullah explains.   
      
   The team of scientists led by Chhana Ullah still has to find out exactly   
   how the molecular mechanism of the positive interaction between salicylic   
   acid and jasmonic acid works in poplar. They also want to know which role   
   PR genes play in poplar and other woody plants. What is certain, however,   
   is that a fundamental knowledge of the positive interaction between   
   salicylic acid and jasmonic acid in poplar and other related trees could   
   make an important contribution to better protecting these plants from pest   
   infestation and disease. Or, as Jonathan Gershenzon notes: "Poplars are   
   known as the trees of the people for their diversified uses by humans,   
   hence the genus name Populus: the Latin name for people. Incredibly   
   fast-growing, poplars are cultivated as short-rotation woody crops and   
   are extremely important of the pulp and paper industry. They are also   
   desirable for biofuels." Improving their protection therefore serves   
   us all.   
      
      
   ==========================================================================   
   Story Source: Materials provided by   
   Max_Planck_Institute_for_Chemical_Ecology. Note: Content may be edited   
   for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Chhana Ullah, Axel Schmidt, Michael Reichelt, Chung‐Jui Tsai,   
         Jonathan Gershenzon. Lack of antagonism between salicylic acid and   
         jasmonate signalling pathways in poplar. New Phytologist, 2022;   
         DOI: 10.1111/nph.18148   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2022/05/220503141350.htm   
      
   --- up 9 weeks, 1 day, 10 hours, 50 minutes   
    * Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)   
   SEEN-BY: 15/0 106/201 114/705 123/120 129/330 331 153/7715 218/700   
   SEEN-BY: 229/110 111 317 400 426 428 470 664 700 292/854 298/25 305/3   
   SEEN-BY: 317/3 320/219 396/45   
   PATH: 317/3 229/426