Characteristics of Partial Sequence of β-lactoglobulin Promoter of Tibetan Yellow Cattle

Objective:The objective of present study was to reveal the molecular basis for the differential expression of β-lactoglobulin(β-Lg) in milks of Tibetan Yellow cattle,yak and Chinese Holstein.Method:Polyacrylamide gel electrophoresis was used to determine the genetic variants of β-Lg and their relative amounts in milk,and partial sequence(375bp) of β-Lg promoter was amplified by PCR and direct sequencing.Result:The relative percentage of β-Lg A in the milk(63.7±2.9%) was higher than β-Lg B in Chinese Holstein carrying heterogous β-Lg,while in the milk of Tibetan Yellow cattle,their relative amounts were similar,with higher variations among individuals.A total of 13 base mutations were detected among the 16 β-Lg promoter sequences assayed,five of which were specific for yaks.Furthermore,a base insertion was observed between-452 and-453 of yak β-Lg promoter.Conclusion:The base mutation at-430 of β-Lg promoter showed allele-specific in Chinese Holstein,but not in Tibetan Yellow cattle.