The expansin gene PttEXPA8 from poplar (Populus tomentosa) confers heat resistance in transgenic tobacco

Expansins are cell wall proteins involved in cell wall loosening and structural remodeling. In this study, we evaluated the transcript levels of 36 expansin genes in Populus tomentosa under heat stress (42 °C) and normal growth conditions (25 °C). One expansin gene, PttEXPA8, significantly up-regulated in leaves under heat stress, was cloned and transformed into tobacco (Nicotiana tobacum). The transgenic and wild-type tobacco plants were subjected to a 10-day heat treatment, and morphological and physiological parameters (relative electrolyte leakage, malondialdehyde content, chlorophyll content, and superoxide dismutase activity) were measured. The results showed that the transgenic plants were more heat-resistant than the wild-type plants. It concluded that PttEXPA8 could be a valuable gene resource conferring heat resistance. The report here contributes to our knowledge of the functions of expansins in woody plants, and also contributes to our knowledge of the molecular mechanism of heat tolerance in poplar.