Identification of MaWRKY40 and MaDLO1 as effective marker genes for tracking the salicylic acid-mediated immune response in bananas

Bananas lie among the world’s most important cash and staple crops but are threatened by various devastating pathogens. The phytohormone salicylic acid (SA) plays a key role in the regulation of plant immune response. Tracking the expression of SA-responsive marker genes under pathogen infection is important in pathogenesis elucidation. However, the common SA-responsive marker genes are not consistently induced in different banana cultivars or different organs. Here, we conducted transcriptome analysis for SA response of a banana cultivar, ‘Pei-Chiao’ (Cavendish, AAA genome), and identified three genes, MaWRKY40, MaWRKY70, and Downy Mildew Resistant 6 (DMR6)-Like Oxygenase 1 (MaDLO1) that are robustly induced upon SA treatment in both the leaves and roots. Consistent induction of these three genes by SA treatment was also detected in both the leaves and roots of bananas belonging to different genome types such as ‘Tai-Chiao No. 7’ (Cavendish, AAA genome), ‘Pisang Awak’ (ABB genome), and ‘Lady Finger’ (AA genome). Furthermore, the biotrophic pathogen cucumber mosaic virus elicited the expression of MaWRKY40 and MaDLO1 in infected-leaves of susceptible cultivars. The hemi-biotrophic fungal pathogen Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) also consistently induced the expression of MaWRKY40 and MaDLO1 in the infected-roots of the Foc TR4-resistant cultivar. These results indicate that MaWRKY40 and MaDLO1 can serve as reliable SA-responsive marker genes for the study of plant immunity in banana. Revealing SA-responsive marker genes provides a stepping-stone for further studies in banana resistance to pathogens.

Yuh Tzean, Bo-Han Hou, Shu-Ming Tsao, Ho-Ming Chen, An-Po Cheng, Elena Gamboa Chen, Wei-Yi Chou, Chih-Ping Chao, Wei-Chiang Shen, Chyi-Chuann Chen, Ming-Chi Lee, Iqra Ashraf, and Hsin-Hung Yeh * (2021) Identification of MaWRKY40 and MaDLO1 as effective marker genes for tracking the salicylic acid-mediated immune response in bananas Phytopathology