Abstract: In the present study,we investigated how temperature stress affected gene expressions of sea cucumber Apostichopus japonicas.Major yolk protein(MYP)gene was selected as a candidate indicator from our former pilot screening study on cold-resistant genes.Two isoforms of MYP namely,MYP1 and MYP2,were both involved,to enhance the reliability of inferences drawn by the current study.Temporal expression features of the two MYPs were surveyed for nine developmental stages(fertilized egg,blastula,gastrula,early auricularia,auricularia,late auricularia,doliolaria,pentactula,juvenile)via RT-PCR.Tissue distribution for adult A.japonicas was studied for seven tissues(respiratory tree,coelomocyte,intestine,muscle,body wall,testis,ovary).Expression profiles of the two MYPs corresponding to a long-term High/Low temperature treatment and a temporal acute cold shock treatment were investigated respectively,with intestine as the target tissue.The two MYPs presented similarities for temporal expression and tissue distribution:gradually enhanced expression from doliolarias stage to juvenile stage;and tissue-ubiquitous(but not in coelomic fluid)expression with greatest abundance in intestine.Interestingly,although the expressions of MYP presented a negative linear relationship with the constant environmental temperature(six times higher for 4 ℃ compared to 20 ℃),a sharp cold shock treatment significantly suppressed them.