The Endophytic Fungus <i>Piriformospora indica</i> Reprograms Banana to Cold Resistance

• Main Authors: Dan Li, David Mahoudjro Bodjrenou, Shuting Zhang, Bin Wang, Hong Pan, Kai-Wun Yeh, Zhongxiong Lai, Chunzhen Cheng
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: International Journal of Molecular Sciences
• Subjects: endophytic fungus; banana cold resistance; antioxidant enzymes; soluble sugar; cold-responsive genes
• Online Access: https://www.mdpi.com/1422-0067/22/9/4973

Banana (<i>Musa</i> spp.), one of the most important fruits worldwide, is generally cold sensitive. In this study, by using the cold-sensitive banana variety Tianbaojiao (<i>Musa acuminate</i>) as the study material, we investigated the effects of <i>Piriformospora indica</i> on banana cold resistance. Seedlings with and without fungus colonization were subjected to 4 °C cold treatment. The changes in plant phenotypes, some physiological and biochemical parameters, chlorophyll fluorescence parameters, and the expression of eight cold-responsive genes in banana leaves before and after cold treatment were measured. Results demonstrated that <i>P. indica</i> colonization reduced the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) but increased the activities of superoxide dismutase (SOD) and catalase (CAT) and the contents of soluble sugar (SS) and proline. Noteworthily, the CAT activity and SS content in the leaves of <i>P. indica</i>-colonized banana were significant (<i>p</i> < 0.05). After 24 h cold treatment, the decline in maximum photochemistry efficiency of photosystem II (<i>F_v</i>/<i>F_m</i>), photochemical quenching coefficient (<i>qP</i>), efficient quantum yield [Y(II)], and photosynthetic electron transport rate (ETR) in the leaves of <i>P. indica</i>-colonized banana was found to be lower than in the non-inoculated controls (<i>p</i> < 0.05). Moreover, although the difference was not significant, <i>P. indica</i> colonization increased the photochemical conversion efficiency and electron transport rate and alleviated the damage to the photosynthetic reaction center of banana leaves under cold treatment to some extent. Additionally, the expression of the most cold-responsive genes in banana leaves was significantly induced by <i>P. indica</i> during cold stress (<i>p</i> < 0.05). It was concluded that <i>P. indica</i> confers banana with enhanced cold resistance by stimulating antioxidant capacity, SS accumulation, and the expression of cold-responsive genes in leaves. The results obtained from this study are helpful for understanding the <i>P. indica</i>-induced cold resistance in banana.