SA及H_2O_2在杨树与溃疡病菌互作中的表达差异

Differential Expression of SA and H_2O_2 between Susceptible and Resistant Poplars Challenged by Botryosphaeria dothidea

以毛白杨和北京杨为试验材料,研究不同杨树接种溃疡病菌后信号分子水杨酸(SA)和过氧化氢(H2O2)的变化差异。结果表明:毛白杨接种后SA与H2O2含量显著上升,72h时内源游离SA含量达到峰值(191.41μg·g-1FW),并伴随H2O2含量的增加和CAT酶活性的降低;而北京杨接种后内源游离SA含量变化不显著(峰值仅为7.83μg·g-1FW),不伴随CAT活性的下降,且H2O2含量与毛白杨相比达到峰值的时间早,峰值低(分别为737.52和306.99nmol·g-1FW),说明不同杨树与溃疡病菌互作体系中SA与H2O2差异显著;同时,克隆获得编码毛白杨水杨酸结合蛋白PtSABP和北京杨PbSABP蛋白的2个基因,氨基酸序列比对分析证明,PtSABP和PbSABP编码的氨基酸与烟草(NtSABP)氨基酸同一性为90%。RT-PCR分析表明:接种后毛白杨SABP基因的表达在6～24h时受到抑制,推测此时SA与SABP结合,抑制SABP的CAT活性,从而促使24h后H2O2含量的显著升高。本试验证明:不同杨树接种溃疡病菌后SA与H2O2变化差异显著,杨树对溃疡病的抗性与其体内SA与H2O2的积累情况有关。

Variations in salicylic acid （SA） and hydrogen peroxide （H202） were analyzed in different resistance poplars （Populus tomentosa and Populus x beijingensis） inoculated with Botryosphaeria dothidea. The results showed that the SA content increased in P. tomentosa, the concentration of endogenous free SA peaked （191.41 μg·g^（-1） FW） at 72 h, which was accompanied with the reduction of CAT activity and increase in H202 content. However, in P. X beijingensis the SA content did not significantly arose （7.83 μg·g^（-1） FW） , and was not accompanied by decreases in CAT activity and H202 content. The H202 peak occurred earlier with lower values compared with P. tomentosa （306.99 nmol·g^（-1） FW vs 737.52 nmol·g^（-1） FW）. The above results indicated there were significant differences in SA and H2O2 in different poplars interacted with B. dothidea. Meanwhile, we isolated and identified full-length coding sequence of PtSABP and PbSABP from P. tomentosa and P. x beijingensis stem eDNAs. The proteins of PtSABP and PbSABP belong to the Catalase_like superfamily, and their sequences are 90% identical to that of tobacco SABP at the amino acid level based on NCBI blast and phylogenetic tree analysis. RT-PCR analysis showed that gene expression of CAT was inhibited in 6 - 24 h after inoculated with B. dothidea, suggesting that SA was bound with SABP at this time, inhibiting CAT activity, thus promoting significant increase in H2O2 content at 24 h after inoculation. The experiments determined that the difference of content of SA and H2O2 in poplars was due to inoculated with B. dothidea, SABP was involved in the disease resistance of poplar, and suggested that the resistance of poplars to B. dothidea would be relevant to the accumulation of SA and H202.