左旋穀醯胺酸抑制bata-aminobutyric acid在阿拉伯芥中引起的抵抗逆境效果和priming的現象

Abstract

Beta-aminobutyric acid (簡稱BABA)是一種人工合成胺基酸，在過往的研究中，可以得知，此胺基酸可以有效促進農作物的抗性。在阿拉伯芥中， BABA確實可以提升植物對病害及逆境的抵抗能力，這種抵抗能力就叫做priming。而priming 這種現象， 除了被荷爾蒙和BABA引起之外， 也有文獻指出，受過逆境的植物，在第二次的逆境之下，會比從沒受過逆境的植物會來的更有抗性。在高等植物中，這種因為Biotic stress或Abiotic stress 造成植物對逆境更有抵抗力的生理意義，我們稱之為stress imprinting。 在我的實驗結果中發現，BABA處理過後的植物，會有生長緩慢(stress-induced morphogenic response, SIMR)以及花青素的累積。而且在microarray data中，BABA活化了stress response gene，所以我們猜想BABA很有可能成一種stress反應。而氨基酸分析BABA處理過後的植物，發現有補脯氨酸以及天門冬醯氨酸的累積， 脯胺酸以及天門冬醯胺酸的累積也是植物stress反應之一。所以我們認為BABA 會對植物造成stress的反應， 進而引發植物對第二次逆境抵抗的能力。令人驚訝的是，穀醯氨酸可以回復BABA對植物造成的影響，像是生長抑制(SIMR)和anthocyanin 累積，對細菌的抗性，還有priming的現象。而這可能是因為平常的生長機制和逆境機制是拮抗的結果，而使加入的glutamine引發的生長機制讓BABA造成的stress imprinting 效果減弱。

The non-protein amino acid beta-aminobutyric acid (BABA) is not produced by plant. BABA has been known for years to be an effective inducer of resistance in various crops. BABA-pretreated Arabidopsis plants challenged with pathogen and abiotic stress will demonstrate enhanced resistance. The induced resistance is often associated with an enhanced capacity to mobilize infection-induced cellular defense responses, this process is called “priming”. Recently, BABA priming was found to be involved in resistance to osmotic and heat stress. The process of priming or hardening involves prior exposure to biotic stress or an abiotic stress making a plant more resistant to future exposure. This indicates the higher plants possess some capacity for memory, or stress imprinting. Microarray data analyses revealed that BABA provokes an accumulation of transcripts involved in both stress signaling and Arabidopsis developmental responses. In addition, BABA was found to activate the stress-induced morphogenic response (SIMR), and also induced anthocyanin accumulation in Arabidopsis. Free amino acids analyses showed that BABA-treated Arabidopsis contain more Asparagine and Proline. Both amino acids are known to accumulate in stressed plants. This observation further indicates that BABA induces a stress imprinting response in Arabidopsis. L-Glutamine is known to counteract the general amino acid inhibition response when supplied to the plant at high concentration. L-Glutamine treatments were found to block BABA-mediated growth inhibition (SIMR), anthocyanin accumulation, priming and bacterial protection. Alteration of the amino acid balance in BABA-treated Arabidopsis also suggests that BABA provokes a stress response by activating the general amino acid inhibition response. Our work suggests that BABA provokes a general amino acid inhibition response in Arabidopsis that leads to stress imprinting.