Browsing by Author "Goodspeed, Danielle"

Now showing 1 - 4 of 4
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    Circadian control of jasmonates and salicylates: The clock role in plant defense
    (Landes Bioscience, 2013) Goodspeed, Danielle; Chehab, E.Wassim; Covington, Michael F.; Braam, Janet
    Plants have evolved robust mechanisms to perceive and respond to diverse environmental stimuli.ﾠ The plant phytohormones jasmonates and salicylates play key roles in activating biotic stress response pathways. Recent findings demonstrate that basal levels of both jasmonates and salicylates in Arabidopsis are under the control of the circadian clock and that clock-controlled jasmonate accumulation may underlie clock- and jasmonate-dependent enhanced resistance of Arabidopsis to Trichoplusia ni (cabbage looper), a generalist herbivore. Here we summarize these findings and provide further evidence that a functional plant circadian clock is required for optimal herbivore defense in Arabidopsis.ﾠ When given a choice to feed on wild-type plants or arrhythmic transgenics, T. ni prefer plants lacking robust circadian rhythms. Altogether these data provide strong evidence for circadian clock enabling anticipation of herbivore attack and thus contributing to overall plant fitness.
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    Keeping the rhythm: light/dark cycles during postharvest storage preserve the tissue integrity and nutritional content of leafy plants
    (BioMed Central, 2015) Liu, John D.; Goodspeed, Danielle; Sheng, Zhengji; Li, Baohua; Yang, Yiran; Kliebenstein, Daniel J.; Braam, Janet
    Background: The modular body structure of plants enables detached plant organs, such as postharvest fruits and vegetables, to maintain active responsiveness to environmental stimuli, including daily cycles of light and darkness. Twenty-four hour light/darkness cycles entrain plant circadian clock rhythms, which provide advantage to plants. Here, we tested whether green leafy vegetables gain longevity advantage by being stored under light/dark cycles designed to maintain biological rhythms. Results: Light/dark cycles during postharvest storage improved several aspects of plant tissue performance comparable to that provided by refrigeration. Tissue integrity, green coloration, and chlorophyll content were generally enhanced by cycling of light and darkness compared to constant light or darkness during storage. In addition, the levels of the phytonutrient glucosinolates in kale and cabbage remained at higher levels over time when the leaf tissue was stored under light/dark cycles. Conclusions: Maintenance of the daily cycling of light and dark periods during postharvest storage may slow the decline of plant tissues, such as green leafy vegetables, improving not only appearance but also the health value of the crops through the maintenance of chlorophyll and phytochemical content after harvest.
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    Plant Defense against Insect Herbivory is Mediated by the Circadian Clock
    (2012) Goodspeed, Danielle; Covington, Michael
    Organisms on earth evolved a circadian clock that matches the planet's 24-hour rotation. The plant clock controls many behaviors and proper entrainment of the clock to the environment leads to a competitive overall growth advantage. Despite the finding that many wound-inducible genes are also circadian regulated, it was uncertain whether this regulation is important for plant defense against herbivorous insects. We found that plants entrained to light-dark cycles 12 hours out of phase with the predator, Trichoplusia ni (cabbage loopers), were more susceptible to T. ni herbivory than plants entrained in phase with T ni . In contrast, arrhythmic clock and jasmonate-deficient mutants were equally susceptible to T. ni herbivory whether entrained in the same or reciprocal 12-hour light-dark cycles. These results suggest that the circadian rhythms, acting through jasmonate signals and the clock, add selective advantage to plants through enhanced anticipation of and defense against herbivory.
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    The Plant Circadian Clock Regulates Biotic Stress Resistance and Defense Hormone Levels
    (2013-11-21) Goodspeed, Danielle; Braam, Janet; Lwigale, Peter Yunju; Masiello, Caroline A.; Matthews, Kathleen S.; Olson, John S.
    Diverse life forms have evolved internal clocks enabling them to monitor time and thereby anticipate the daily environmental changes caused by the earth’s rotation. The plant circadian clock regulates expression of about one-third of the Arabidopsis genome, yet the physiological relevance of this regulation is not fully understood. Here we show that the circadian clock, acting with hormone signals, provides selective advantage to plants through anticipation of and enhanced defense against herbivory and pathogen infection. I found that plants entrained in-phase with the herbivore Trichoplusia ni (T. ni) are more resistant than plants entrained out-of-phase. Similarly, when plants are inoculated with Botrytis cinerea (B. cinerea), the time-of-day at which the inoculation initially occurred significantly affects the rate of infection. Both the circadian clock and jasmonates are required for resistance to herbivory and time-of-day resistance to pathogen infection. Jasmonate and salicylate accumulation is circadian regulated, and accumulation patterns are in opposite phase to each other. I also demonstrate that the circadian clock of post-harvest cabbage (Brassica oleracea) is entrainable by light-dark cycles and results in enhanced herbivore resistance. In addition, entrainment of Arabidopsis plants and post-harvest cabbage causes cyclical accumulation of metabolites that function in plant defense. Finally, I show that the phenomenon of post-harvest entrainment and enhanced herbivore resistance is widespread among diverse crops. The evolution of the plant circadian clock not only provides a strong physiological advantage in pest defense but also can enhance the nutritional value of plant-derived food.