Expansins, a group of cell wall-loosening proteins, are involved in cell-wall loosening and cell enlargement in a pH-dependent manner. According to previous study, they were involved in plant growth and abiotic stress responses. However, information on the biological function of the expansin gene in moso bamboo is still limited. In this study, we identified a total of 82 expansin genes in moso bamboo, clustered into four subfamilies (α-expansin (EXPA), β-expansin (EXPB), expansin-like A (EXLA) and expansin-like B (EXPB)). Subsequently, the molecular structure, chromosomal location and phylogenetic relationship of the expansin genes of Phyllostachys edulis (PeEXs) were further characterized. A total of 14 pairs of tandem duplication genes and 31 pairs of segmented duplication genes were also identified, which may promote the expansion of the expansin gene family. Promoter analysis found many cis-acting elements related to growth and development and stress response, especially abscisic acid response element (ABRE). Expression pattern revealed that most PeEXs have tissue expression specificity. Meanwhile, the expression of some selected PeEXs was significantly upregulated mostly under abscisic acid (ABA) and polyethylene glycol (PEG) treatment, which implied that these genes actively respond to expression under abiotic stress. This study provided new insights into the structure, evolution and function prediction of the expansin gene family in moso bamboo.

The selection of superior lines is extremely important to improve the utilization rate and economic value of bamboo. In this research, 120 anther-regenerated bamboo lines were planted in the field, and the survival rate reached 84.2% one year after planting. During five years of observations, we continuously measured and recorded the number of shoots and the size of the new bamboo of these regenerated lines. The results showed that there were considerable differences in culm size and growth rate among the different lines. After comprehensive evaluation, we found that one of the lines (P82) had obvious advantages in culm size and growth rate compared with the others. The chromosome ploidy of line P82 and the other three lines (P38, P84, and P34) was detected. It was found that P82 was hexaploid, while the other three lines were dodecaploid. Nutritional components of the P82 shoots were further detected. The results showed that the content of soluble sugar was 1.4%, the content of free amino acid was 3.5 g·kg⁻¹ (FW, fresh weight), and the content of protein was 14.8 g·kg⁻¹ (FW), and there were no significant differences compared with the local wild mature bamboo. Anatomical analysis showed that the vascular bundle size of the line P82 (hexaploid) was significantly larger than that of line P38 (dodecaploid), and the length of parenchyma cells in the culm wall of line P82 was similar to that of line P38, however, the cell width of line P82 was significantly wider than that of line P38. In this study, the breeding of superior lines of regenerated bamboo plants from an anther culture was realized, which provided an example for a new method for selecting superior lines from an anther culture, and also enriched the resources of superior lines of D. latiflorus.