圖1. 美國南加州大學一項研究揭露，植物利用生理時鐘及特定蛋白質， ABF3來應付環境壓力，提供了開發抗乾旱及土壤鹽分作物的新方法。該項研究為基改作物鋪路，潛在上能提高面對氣候變遷的抵抗能力及產量。
A USC study reveals that plants use their circadian clocks and a specific protein, ABF3, to manage environmental stress, offering new approaches to develop crops resistant to drought and soil salinity. This research paves the way for genetically improved crops, potentially boosting resilience and yield in the face of climate change.
Recent research reveals that plants employ their internal circadian rhythms to adapt to fluctuations in water availability and salt levels, presenting a novel strategy for developing crops that can withstand drought conditions.
最近的研究揭露，植物利用其內部晝夜節律，來適應可用水分及鹽分含量的波動。這為開發能經得起乾旱條件的作物，提供了一種新策略。
Climate change is currently impacting agricultural productivity and could eventually pose a considerable risk to global food security. Developing crops that are more resilient, capable of withstanding conditions such as drought or elevated soil salinity, is becoming an urgent need.
目前，氣候變遷正在影響農業生產力，且最終可能對全球糧食安全，構成相當大的風險。開發更有適應力、能經得起諸如乾旱或土壤鹽分升高等條件的作物，正成為一種迫切需求。
A new study from the Keck School of Medicine of USC, funded in part by the National Institutes of Health, reveals details about how plants regulate their responses to stress that may prove crucial to those efforts. Researchers found that plants use their circadian clocks to respond to changes in external water and salt levels throughout the day.
一項來自美國南加州大學凱克醫學院，部分由美國國家衛生研究院所資助的新研究，揭露了有關植物如何調節其對壓力，至關重要反應的細節。研究人員發現，植物利用其生理時鐘，來對全天外部水分及鹽分含量的變化作出反應。
That same circuitry—an elegant feedback loop controlled by a protein known as ABF3—also helps plants adapt to extreme conditions such as drought. The results were recently published in the journal Proceedings of the National Academy of Sciences.
那同樣的廻路體系(一種由被通稱為ABF3蛋白質控制的極佳反饋迴路)也有助於，植物適應諸如乾旱等極端條件。此些研究結果，最近發表於《美國國家科學院院刊》雜誌。
“The bottom line is plants are stuck in place. They can’t run around and grab a drink of water. They can’t move into the shade when they want to or away from soil that has excess salt. Because of that, they’ve evolved to use their circadian clocks to exquisitely measure and adapt to their environment,” said the study’s senior author, Steve A. Kay, PhD, University and Provost Professor of Neurology, Biomedical Engineering and Quantitative Computational Biology at the Keck School of Medicine and Director of the USC Michelson Center for Convergent Bioscience.
該研究資深撰文人，美國南加州大學凱克醫學院神經病學、生物醫學工程及定量計算生物學的大學暨教務長教授，兼南加州大學邁克爾遜融合生物科學中心主任，Steve A. Kay博士宣稱：「關鍵是植物被固定於原地。它們無法到處吸收水分。當想進入陰涼處，或遠離含鹽分過多的土壤時，它們無法移動。因為那樣，它們已經演化出使用生理時鐘，來精確調節及適應其環境。」
圖2.擬南芥幼苗，在對水分壓力作出反應，使生理時鐘信息基因表現時的生物發光影像。
Bioluminescent image of Arabidopsis seedlings expressing circadian clock reporter genes in response to water stress.
The findings build on a long line of research from Kay’s lab on the role of circadian clock proteins in both plants and animals. Clock proteins, which regulate biological changes over the course of the day, may provide a shrewd solution to an ongoing challenge in crop engineering.
此些研究發現，以來自Kay的實驗室，針對生理時鐘蛋白質，在動、植物兩者中之角色的長期研究為基礎。在一天的過程中，調節生物變化的時鐘蛋白質，可能對作物設計上持續存在的挑戰，提供一種精明的解決方案。
Creating drought-resistant plants is difficult, because plants respond to stress by slowing their own growth and development—an overblown stress response means an underperforming plant.
創造抗旱植物是困難的。因為，植物藉由減緩自身的生長及發育，來對壓力作出反應。過度的壓力反應意味著，植物表現不佳。
“There’s a delicate balance between boosting a plant’s stress tolerance while maximizing its growth and yield,” Kay said. “Solving this challenge is made all the more urgent by climate change.”
Kay宣稱：「在增強植物的壓力耐受性與最大化其生長及產量間，有一種脆弱的平衡。氣候變遷使得解決該項挑戰，變得更加緊迫。」
Previous plant biology research showed that clock proteins regulate about 90% of genes in plants and are central to their responses to temperature, light intensity and day length, including seasonal changes that determine when they flower.
先前的植物生物學研究顯示，生理時鐘蛋白質調節植物中大約90%的基因，且對於植物對溫度、光線強度及日照長度之反應是重要部分，包括決定植物何時開花的季節變化。
But one big outstanding question was whether and how clock proteins control the way plants handle changing water and soil salinity levels.
不過，一項未解決的大問題是，生理時鐘蛋白質是否及如何控制，植物應對水分與土壤鹽分含量變化的方式。
To explore the link, Kay and his team studied Arabidopsis, a plant commonly used in research because it is small, has a rapid life cycle, a relatively simple genome and shares common traits and genes with many agricultural crops.
為了探索此關聯性，Kay及其團隊研究了擬南芥。這是一種常被用於研究的植物。因為它體積小，具有迅速的生命週期，基因體相對簡單且與許多農作物，共同具有共同的特徵及基因。
They created a library of all of the more than 2000 Arabidopsis transcription factors, which are proteins that control the way genes are expressed under different circumstances.
他們創建了一個，擬南芥在不同情況下，控制基因表現方式，全數多於2千個蛋白質的轉錄因子庫。
Transcription factors can provide key insights about regulation of biological processes. The researchers then built a data analysis pipeline to analyze each transcription factor and search for associations.
轉錄因子能提供，有關調節生物變化過程的重要洞察力。之後，此些研究人員建立了一個數據分析途徑，來分析每一轉錄因子，並尋找關聯性。
“We got a really big surprise: that many of the genes the clock was regulating were associated with drought responses,” Kay said, particularly those controlling the hormone abscisic acid, a type of stress hormone that plants produce when water levels are very high or very low.
Kay宣稱：「我們獲得了一個非常大的驚訝：亦即，生物時鐘調節的諸多基因，與乾旱反應有所關聯。」特別是，那些控制脫落酸激素的基因。脫落酸是當水分含量非常高或非常低時，植物產生的一種壓力荷爾蒙。
The analysis revealed that abscisic acid levels are controlled by clock proteins as well as the transcription factor ABF3 in what Kay calls a “homeostatic feedback loop.”
分析揭露了，在Kay稱為“體內平衡的反饋廻路”中，脫落酸含量，除了轉錄因子ABF3之外，也由時鐘蛋白質所控制。
Over the course of a day, clock proteins regulate ABF3 to help plants respond to changing water levels, then ABF3 feeds information back to clock proteins to keep the stress response in check. That same loop helps plants adapt when conditions become extreme, for instance during a drought. Genetic data also revealed a similar process for handling changes in soil salinity levels.
在一天的過程中，生理時鐘蛋白質調節ABF3，以協助植物應對變化之水分含量，然後ABF3將信息回饋到生理時鐘蛋白質，來控制壓力反應。當條件變得極端時，譬如在乾旱期間，同樣的廻路有助於植物適應。遺傳數據也揭露了，處理土壤鹽分含量變化的類似過程。
“What’s really special about this circuit is that it allows the plant to respond to external stress while keeping its stress response under control, so that it can continue to grow and develop,” Kay said.
Kay宣稱：「有關此迴路的真正特殊處是，它使植物得以對外部壓力作出反應，同時保持其壓力反應於控制下，以便使植物能夠繼續生長及發育。」
The findings point to two new approaches that may help boost crop resilience. For one, agricultural breeders can search and select for naturally occurring genetic diversity in the circadian ABF3 circuit that gives plants a slight edge in responding to water and salinity stress. Even a small increase in resilience could substantially improve crop yield on a large scale.
此些研究發現指出了兩種，可能有助於增強作物適應力的新方法。舉個例，在晝夜節律的ABF3迴路中，農業育種者們能搜尋及選擇，在應對水分及鹽分壓力上，賦予植物輕微優勢之自然發生的遺傳多樣性。在適應力方面，即使小幅提高，實質上也能大幅改善作物產量。
Kay and his colleagues also plan to explore a genetic modification approach, using CRISPR to engineer genes that promote ABF3 in order to design highly drought-resistant plants.
為了設計高度抗旱的植物，Kay及其同僚們也計劃探索一種，使用群聚、規律性間隔開的短迴文結構複製(CRISPR：Clustered Regularly Interspaced Short Palindromic Repeat)來工程改造，促進ABF3的基因改造方法。
“This could be a significant breakthrough in thinking about how to modulate crop plants to be more drought resistant,” Kay said.
Kay宣稱：「在思考如何調節農作物成為更抗旱上，這或許是一項重大突破。」
網址：https://scitechdaily.com/engineering-the-super-plants-of-tomorrow-the-key-lies-in-circadian-rhythms/
翻譯：許東榮
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