ANALYSIS OF DEFENSE GENE EXPRESSION IN RESPONSE TO THE INFECTION OF FUSARIUM OXYSPORUM F.SP. CUBENSE TR4 (FOC TR4) IN BANANA (MUSA ACUMINATA L. AAA GROUP, CV. AMBON KUNING)

• Main Author: Utami, Ita
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/85257
• Institution: Institut Teknologi Bandung

Ambon Kuning banana (Musa acuminata, AAA group) is one of the banana cultivars widely cultivated and consumed in Indonesia. However, the production of this banana often faces challenges due to Fusarium wilt disease caused by the pathogen Fusarium oxysporum f.sp. cubense (Foc), particularly the tropical race 4 strain (Foc TR4). Numerous studies have reported that Foc TR4 has already infected various types of local banana cultivars, including Ambon Kuning. Investigating the expression profiles of resistance-related genes can provide crucial insights into the plant's response to Foc TR4 infection. In the plant's defense mechanisms against pathogen infection, salicylic acid (SA) is a key phytohormone that can induce the plant's defense system. Therefore, this study aims to obtain the expression profile of resistance-related genes in Ambon Kuning bananas involved in the salicylic acid signaling pathway during Foc TR4 infection. The genes include phenylalanine ammonia lyase (PAL), non-expresser of PR (NPR1, NPR5, and NPR6), TGA2 transcription factor (TGA2), and pathogenesis-related genes (PR1 and PR5). Gene expression was observed at 6, 24, and 72 hours post-infection (hpi). In this study, quantitative polymerase chain reaction (qPCR) was used to analyze the expression of the seven target genes related to the SA signaling pathway. The results showed that genes involved in SA biosynthesis and signaling, namely PAL, NPR1, NPR5, and NPR6, exhibited a similar expression pattern, with an increase in expression at 6 hours post-infection, followed by a decrease at 24 and 72 hpi. This indicates that during the early stages of Foc TR4 infection, SA biosynthesis and signaling occur to activate the plant's defense system. Furthermore, the expression of TGA2, a transcription factor that activates downstream SA responses, including pathogenesis-related (PR) genes, significantly increased at all three observation times. This is because the TGA2 transcription factor is not only activated by SA signaling but can also be triggered by reactive oxygen species (ROS) signaling, which occurs when the plant experiences stress, such as pathogen infection. On the other hand, the target genes of the TGA2 transcription factor, namely PR1 and PR5, showed an increase in expression at 6 and 72 hpi but a decrease in expression at 24 hpi. The suppression of these resistance genes in the salicylic acid pathway may also be caused by effector proteins secreted by Foc TR4, which can inhibit the plant's defense system.