外源添加山梨醇和海藻糖对意大利蜜蜂抗寒性能的影响

Effects of Exogenous Trehalose and Sorbitol on Cold Resistance of Apis mellifera ligustica

本试验旨在通过测定意大利蜜蜂(简称意蜂)体内山梨醇、海藻糖等相关生化物质含量、抗氧化酶活性及抗寒基因表达的变化,探究外源添加山梨醇和海藻糖在蜜蜂抗寒过程中的作用机制。从意蜂姊妹蜂群中随机选取900只刚出房的蜜蜂,随机分成6组,每组3个重复,每个重复50只蜜蜂,分别饲喂蔗糖溶液(对照)、海藻糖溶液和山梨醇溶液。6组均于常温(30℃)下饲养12 d,其中3组在饲喂12 d后进行冷处理(4℃冷驯化2 h)。饲喂12 d后立即测定蜜蜂过冷却点、冰点,比较其抗寒性能差异。然后分别测定蜂体游离水、糖原、脂肪含量、山梨醇脱氢酶(SDH)、海藻糖酶(THL)活性以及海藻糖-6-磷酸合成酶(TPS)、SDH mRNA相对表达量的差异;另取900只意蜂,按照以上分组饲养,用于测定血淋巴中小分子糖醇含量。结果表明:1)与对照组相比,山梨醇组和海藻糖组过冷却点分别降低0.65(P<0.05)、0.41℃(P<0.05)。2)与对照组相比,常温以及冷处理条件下,山梨醇组和海藻糖组蜂体游离水含量变化不显著(P>0.05)。3)与对照组相比,常温以及冷处理条件下,海藻糖组和山梨醇组蜂体内脂肪含量变化不显著(P>0.05),而糖原含量显著提高(P<0.05)。4)与对照组相比,常温以及冷处理条件下,山梨醇组和海藻糖组血淋巴中葡萄糖含量显著增加(P<0.05);常温条件下,山梨醇组血淋巴中果糖含量显著提高(P<0.05),而冷处理条件下,海藻糖组血淋巴中果糖含量显著降低(P<0.05);常温条件下,山梨醇组血淋巴中山梨醇含量显著增加(P<0.05),而冷处理条件下,结果差异不显著(P>0.05)。5)与对照组相比,常温以及冷处理条件下,山梨醇组和海藻糖组蜂体SDH和THL活性均显著提高(P<0.05)。6)与对照组相比,常温以及冷处理条件下,山梨醇组SDH mRNA相对表达量显著上调(P<0.05);常温条件下,海藻糖组TPS mRNA相对表达量显著下调(P<0.05)。综上所述,在室内饲养的离群意蜂外源添加山梨醇、海藻糖显著降低了意蜂的过冷却点、冰点,进而提高了抗寒性。山梨醇和海藻糖通过调节意蜂血淋巴中小分子糖醇含量,以及与山梨醇、海藻糖代谢通路相关的基因表达量来提高蜜蜂的抗寒性。

To study the effects of exogenous sorbitol and trehalose on the cold resistance of Apis mellifera ligustica,the contents of sorbitol,trehalose and other related biochemical substances in honeybees,the changes of antioxidant enzyme activity and the expression of cold-resistant genes were measured to explore the possible physiological and biochemical mechanisms in the cold-resistant process of honeybees.From the A.m.ligustica sister colony,900 young bees which were just out of the house were randomly selected and divided into 6 groups with 3 replicates per each group and 50 bees per replicate.The bees were fed sucrose solution,trehalose solution and sorbitol solution,respectively.All the 6 groups were fed at normal temperature(30℃)for 12 days,after feeding for 12 days,three of the groups were cold treated(4℃cold training for 2 h).After treatment,supercooling point,freezing point were detected for comparing the difference of cold resistance;the contents of free moisture,glycogen,fat,the activities of sorbitol dehydrogenase(SDH)and trehalase(THL),and the mRNA relative expession levels of trehalose monophosphate synthase(TPS)and SDH were determined.Another 900 young bees were bred according to the above groups for the determination of small molecular sugar alcohols contents in hemolymph.Results showed as follows:1)compared with the control group,supercooling point in sorbitol group and trehalose group reduced by 0.65(P<0.05)and 0.41℃(P<0.05).2)Compared with the control group,under normal temperature and cold treatment conditions,the content of free moisture in sorbitol group and trehalose group had no significant change(P>0.05).3)Compared with the control group,under normal temperature and cold treatment conditions,the body fat content in sorbitol group and trehalose group had no significant change(P>0.05),but the glycogen content significantly increased(P<0.05).4)Compared with the control group,under normal temperature and cold treatment conditions,glucose content in hemolymph in sorbitol group and trehalose group increased significantly(P<0.05);under normal temperature condition,the content of fructose in hemolymph in sorbitol group significantly increased(P<0.05),under cold treatment condition,the content of fructose in hemolymph in trehalose group decreased significantly(P<0.05);under normal temperature condition,the sorbitol content in hemolymph in sorbitol group increased significantly(P<0.05),while under cold treatment condition,the results showed no significant difference(P>0.05).5)Compared with the control group,under normal temperature and cold treatment conditions,the SDH and THL activities in sorbitol group and trehalose group significantly increased(P<0.05).6)Compared with the control group,under normal temperature and cold treatment conditions,the mRNA relative expression level of SDH in sorbitol group significantly up-regulated(P<0.05).Under normal temperature condition,the mRNA relative expression level of TPS in trehalose group significantly decreased(P<0.05).To sum up,the exogenous addition of sorbitol and trehalose in the diets of bees raised in the room significantly reduce the supercooling point and freezing point of bees,thus improving the cold tolerance.Sorbitol and trehalose improve the cold tolerance of bees by regulating the content of small molecule sugar alcohol in hemolymph and the expression of genes related to sorbitol and trehalose metabolic pathways.