Objective  To study the function of auxin transporter PIN gene family in the adaptation of soybean (Glycine max) roots to low phosphorus stress.

Method  A total of 23 GmPIN family members of soybean were conducted evolutionary tree and expression pattern analyses, so as to analyze the GmPIN2bfunction.

Result  The 23 GmPIN family members of soybean were scattered in seven different sub-families, among which GmPIN2a, GmPIN2b and GmPIN9a, GmPIN9d were in the same subfamily as Arabidopsis thaliana AtPIN2. Different GmPIN family members had different tissue expression locations in soybean and their expression patterns regulated by low phosphorus were different. Among them, the expression level of GmPIN2b in soybean roots was significantly up-regulated after low phosphorus stress for six days. The complement expression of GmPIN2b could partially restore the phenotype of Atpin2 mutants. The fresh weight and main root length of transgenic plants expressing GmPIN2b were significantly higher than those of Atpin2 mutant under both low or high phosphorus conditions. Moreover, the complement expression of GmPIN2b also significantly increased the number of primary lateral roots of Atpin2 mutant in low phosphorus treatment, and increased the sensitivity of the root system to gravity in high phosphorus treatment.

Conclusion  GmPIN2b plays an important regulatory role in the process of root morphogenesis in response to low phosphorus stress.