Chitosan suppresses the expression level of WRKY17 on red chili (Capsicum annuum) plant under drought stress Muhammad Abdul Aziz 1, 3 , Rizkita Rachmi Esyant 1,* , Karlia Meitha 1,2 , Fenny Martha Dwivany 1, 2 , and Hany Husnul Chotmah 1 1 School of Life Sciences and Technology, Insttut Teknologi Bandung, West Java, Indonesia 2 Research Center for Nanosciences and Nanotechnology, Insttut Teknologi Bandung, West Java, Indonesia 3 Indonesian Research Insttute For Biotechnology and Bioindustry, Jl. Taman Kencana No. 1 Bogor, West Java, Indonesia 16128 *Corresponding author: rizkita@sith.itb.ac.id SUBMITTED 23 March 2020 REVISED 5 May 2020 ACCEPTED 22 May 2020 ABSTRACT Chili pepper plays a signifcant role in the global market. However, the producton is ofen impeded by drought stress involving WRKY genes as the defense regulator. Chitosan is considered as a promising alternatve fertlizer and defense elicitor. Hence, this study aimed to determine the role of chitosan in improving plant growth and survival of red chili pepper against drought stress. At the onset of the generatve phase, chili plants were subjected to 1 mg/mL chitosan, 50% drought, or chitosan‐drought treatment. Observatons were made on several growth parameters, opened stomata, and WRKY gene expression. The results showed that chitosan‐drought treatment decreased plant growth and yielded signifcantly. The percentage of opened stomata was recorded at 0.56‐fold lower than control. It was followed by the decrease of the relatve expression of WRKY17 and WRKY53 genes up to 0.56 and 0.72‐fold lower than control, respectvely. Therefore, we suggested that the double treatment of chitosan‐drought might decrease plant growth performance but increase the defense system by suppressing the expression level of the WRKY17 gene. Interestngly, the drought treatment signifcantly increased WRKY17 expression level up to 7‐fold higher than control. Hence, it was suggested that WRKY17 has a specifc role in response to drought stress. KEYWORDS red chili; chitosan; drought; growth performance; gene expression Indonesian Journal of Biotechnology VOLUME 25(1), 2020, 52‐60 | RESEARCH ARTICLE 1. Introducton Red chili pepper (Capsicum annuum) is a widely domes ticated and very popular plant throughout the world, rou tinely consumed by about onefourth of the global popu lation (Khan et al. 2014). In Indonesia, this plant is one of the most prioritized vegetables with a high economic value used for daily consumption, food industries, and ex port commodities. In 2014, the total production was about 1.075 million tons or around 9.02% of Indonesia’s national vegetable production (KEMENTAN 2015). The average demand for this commodity in the urban area is around 66,000 tons per month increasing up to 20% at a certain period. However, red chili production in Indonesia fluctu ates from time to time and is often unable to meet the mar ket needs. In addition to pathogen infection, the decrease of production is also caused by limited hydration. For in stance, the phenomenon of drought in the Semarang dis trict caused 500 Ha of agricultural land to be affected, and 72 hectares experienced crop failure in 2014 (KEMEN TAN 2016). If this phenomenon occurs in a prolonged pe riod, it might inhibit plant growth or death, resulting in low productivity, increased prices, and decreased export commodities. Drought is the most frequent abiotic stress experienced by plants due to global climate change in recent years (Khan et al. 2014). In general, the plant will respond to water stress by synthesizing abscisic acid (ABA) as the defense regulator, which leads to closed stomata. It aims to reduce the rate of transpiration, but it also impacts de creasing photosynthesis rate, resulting in decreased plant growth and productivity (Iriti et al. 2009). Under stress conditions, a plant can carry out the various defense mech anisms through molecular, cellular, and biochemical inte gration (Khan et al. 2014). WRKY is a transcription factor known to play a role in the abscisic acid (ABA) and jas monic acid (JA) signaling pathways in response to drought stress. WRKY is characterized by the existence of one or two conserved WRKY domains in the Nterminus and a zinc finger motif in the Cterminus. These two elements are crucial for the affinity of WRKY protein binding with the consensus sequence (C/T) TGAC (C/T) called Wbox. There are 74 kinds of WRKY protein found in Arabidopsis and classified into three groups based on the number and Indones J Biotechnol 25(1), 2020, 52‐60 | DOI 10.22146/ijbiotech.55016 www.jurnal.ugm.ac.id/ijbiotech Copyright © 2020 THE AUTHOR(S). This artcle is distributed under a Creatve Commons Atributon‐ShareAlike 4.0 Internatonal license.