Mode of Action of K28822, a Novel Bleaching Herbicide

국문 초록 (Abstract)

본 연구에서는 식물에 처리했을 때 백화(whitening)를 유도하는 신규화합물 K28822의 작용기작을 구명하기 위하여 제반 실험을 수행하였다. 먼저 사전에 보고된 LEMPA(Lemna paucicostata) growth assay와 카로티노이드 성분의 흡광스펙트럼 변화를 조사한 결과, Type C의 생장반응, 엽상체에서의 band-like necrosis 없음, stipe의 신장 유도, 선명한 백색칼라 발현, 무처리구 대비 Car/Chl (%) 감소, 카로티노이드성분의 흡광도 패턴에 있어서 무처리 대비 250–300nm 흡광도 증 가/400–500nm 흡광도 감소, 276nm < 286nm 흡광도 피크 등의 특징을 보여 phytoene desaturase (PDS) 저해제인 picolinafen과 정확히 동일한 제초증상 및 생리반응을 나타내었다. 그리고 벼(Oryza sativa)를 이용하여 생장저해 및 회복시험을 실시한 결과, K28822 처리농도가 증가하면 백화와 함께 유묘길이가 증가되는 경향이었고, 4-hydroxyphenyl pyruvic acid와 homogentisic acid를 첨가하였을 때, 광합성색소 함량이 모두에서 어느 정도 회복되는 경향을 보여 4-hydroxyphenyl pyruvate dioxygenase 저해제인 sulcotrione과는 달리, PDS 저해제인 norflurazon에서와 동일한 생리반응을 보여주었다.
아울러 PDS 단백질 수준에서의 K28822의 결합여부를 In silico molecular docking analysis를 통하여 실시한 결과, 높은 binding affinity를 가지면서( < - 7.28 kcal/mol) 기존 제초제들(norflurazon, picolinafen, rimisoxafen)과 유사한 위치에 결합되는 양상을 보였다. 이들의 실험결과를 종합해 보았을 때, K28822은 carotenoid 생합성과정의 PDS를 저해함으로써 제초작용을 나타낸다고 여겨진다.

다국어 초록 (Multilingual Abstract)

In this study, a series of experiments were conducted to elucidate the mode of action of a novel compound, K28822, which induces bleaching symptoms in plants. Initially, based on a reported Lemna paucicostata (LEMPA) growth assay and analysis of absorption spectra changes in carotenoid components, K28822 exhibited characteristic features of Type C growth inhibition. These included an absence of band-like necrosis in the fronds, induction of stipe elongation, and appearance of a distinct white coloration. In addition, the carotenoid:chlorophyll ratio (Car/Chl, %) was observed to be lower than that in the untreated control. The carotenoid absorption spectrum showed increased absorbance in the 250–300 nm range and decreased absorbance in the 400–500 nm range relative to that of the control, along with an absorption peak pattern of 276–286 nm. These features closely matched the herbicidal symptoms and physiological responses of the phytoene desaturase (PDS) inhibitor picolinafen. Furthermore, growth inhibition and recovery assays using Oryza sativa (rice) revealed that increasing concentrations of K28822 enhanced the bleaching effect, along with a tendency for increased seedling elongation. When 4-hydroxyphenylpyruvic acid and homogentisic acid were added, partial recovery of photosynthetic pigment content occurred in both cases. Unlike the response typically associated with the 4-hydroxyphenylpyruvate dioxygenase inhibitor sulcotrione, K28822 demonstrated physiological responses consistent with those of the PDS inhibitor norflurazon. In addition, in silico molecular docking analysis was performed to evaluate the binding of K28822 to the PDS protein. The results indicated a favorable binding affinity (< -7.2 kcal/mol), with K28822 occupying a binding site similar to those of known herbicides such as norflurazon, picolinafen, and rimisoxafen. Collectively, these findings suggest that K28822 exerts its herbicidal activity by inhibiting phytoene desaturase enzymes in the carotenoid biosynthesis pathway.