Wenbin Liao, Jie Cai, Haixia Xu, Yilin Wang, Yingjie Cao, Mengbin Ruan, Songbi Chen, Ming Peng

Front Plant Sci.; 2023 Feb 13; 13:1101821. doi: 10.3389/fpls.2022.1101821. eCollection 2022.

Abstract

The reactive oxygen species (ROS) signal regulates stress-induced leaf abscission in cassava. The relationship between the function of the cassava transcription factor bHLH gene and low temperature-induced leaf abscission is still unclear. Here, we report that MebHLH18, a transcription factor, involved in regulating low temperature-induced leaf abscission in cassava. The expression of the MebHLH18 gene was significantly related to low temperature-induced leaf abscission and POD level. Under low temperatures, the levels of ROS scavengers in different cassava genotypes were significantly different in the low temperature-induced leaf abscission process. Cassava gene transformation showed that MebHLH18 overexpression significantly decreased the low temperature-induced leaf abscission rate. Simultaneously, interference expression increased the rate of leaf abscission under the same conditions. ROS analysis showed a connection between the decrease in the low temperature-induced leaf abscission rate caused by MebHLH18 expression and the increase in antioxidant activity. A Genome-wide association studies analysis showed a relationship between the natural variation of the promoter region of MebHLH18 and low temperature-induced leaf abscission. Furthermore, studies showed that the change in MebHLH18 expression was caused by a single nucleotide polymorphism variation in the promoter region upstream of the gene. The high expression of MebHLH18 led to a significant increase in POD activity. The increased POD activity decreased the accumulation of ROS at low temperatures and the rate of leaf abscission. It indicates that the natural variation in the promoter region of MebHLH18 increases antioxidant levels under low temperatures and slows down low temperature-induced leaf abscission.

See https://pubmed.ncbi.nlm.nih.gov/36860206/

Figure 1

The levels of reactive oxygen scavengers significantly different among cassava genotypes during low temperature-induced leaf abscission. (A–C) Peroxidase (POD) (A), Superoxide dismutase (SOD) (B) and Catalase (CAT) (C) activities in cassava were detected among cassava genotypes during low temperature-induced leaf abscission. CK-L: Leaf control; LT-L: Leaf treated at 4°C for 24 hours; CK-R: root control; LT-R: root treated at 4°C for 24 hours. In low temperature-induced cassava leaf abscission, significant differences in reactive oxygen species scavengers were detected between cassava genotypes. Cassava grown for 120 days was selected as the experimental material. The cassava plants with consistent growth were selected for low-temperature treatment. After the plants were treated at 4°C for 24 hours, the control plants were placed in the greenhouse for normal growth. The treated and control plants were placed in the greenhouse simultaneously for growth recovery. Samples were taken after 10 days of growth recovery. The leaves were collected from the upper, middle, and lower parts of the four plants. The roots of the four plants were mixed and frozen in liquid nitrogen and stored at −80°C. During low temperature-induced leaf abscission, POD, SOD and CAT activities in cassava were detected. The value is represented as mean ± standard error (n=40).