糖分含量对番茄叶片Pst DC3000抗性的影响及其机理

研究糖代谢对番茄叶片细菌性叶斑病(Pst DC3000)抗性的影响及其可能的生理生化机制,为抗病番茄新品种的选育提供参考。以糖代谢特征不同的早上取样叶片(早8:00取样)和晚上取样叶片(晚6:00取样)为材料,测定离体接种后不同时期(0、24、48 h)上述两种叶片在Pst DC3000抗性、细菌密度、可溶性糖和淀粉含量、转化酶活性、水杨酸(SA)和茉莉酸(JA)含量、细胞死亡和H₂O₂积累方面的差异。结果表明,和早上取样叶片相比,晚上取样叶片对Pst DC3000具有更高的抗性,表现为较轻的病斑和细胞死亡现象,同时叶片内的细菌密度也极显著(P≤0.01)降低。此外,和早上取样叶片相比,晚上取样叶片在接种后具有更高的淀粉含量(0~48 h)、葡萄糖含量(0、24 h)和果糖含量(24、48 h),但在蔗糖含量上无显著差异。对3种转化酶活性的测定表明,晚上取样叶片的细胞壁转化酶(CWIN)活性在接种后0、48 h显著(P≤0.05)低于早上取样叶片,而细胞质转化酶(CIN)活性在接种后24、48 h则显著(P≤0.05)高于早上取样叶片,液泡转化酶(VIN)活性在两种叶片之间无显著差异。最后,和早上取样叶片相比,晚上取样叶片具有相对较少的H₂O₂积累(48 h)和显著(P≤0.05)较高的游离态SA和JA含量(48 h)。总之,和早上取样叶片相比,晚上取样叶片具有较高淀粉、己糖含量和CIN活性,以及较低的CWIN活性,这可能是晚上取样叶片具有较高SA和JA含量,以及较少H₂O₂积累和细胞死亡的重要原因,从而使得晚上取样叶片对Pst DC3000的抗性提高。

Effects of sugar content on resistance of tomato leaf to bacterial leaf spot and possible underlying mechanisms

The study was conducted to study the effect of sugar metabolism on the resistance of tomato to bacterial leaf spot disease (Pst DC3000) and the physiological and biochemical mechanisms possibly involved, which could benefit the breeding of new tomato varieties with high resistance to Pst DC3000. To get leaves with different characteristics in sugar metabolism,tomato leaves were sampled at two different time (8:00 AM and 6:00 PM), which were referred to as morning-sampled leaves and evening-sampled leaves, respectively. These two kinds of leaves were in vitro inoculated with Pst DC3000 and then tested at 0, 24 and 48 h after inoculation for several indicators, including Pst DC3000 resistance, bacterial density, the content of soluble sugar and starch, invertase activities, the content of salicylic acid (SA) and jasmonic acid (JA), cell death incidence and H₂O₂ accumulation. It was found that, as compared with the morning-sampled leaves, the evening-sampled leaves showed higher resistance to Pst DC3000 as revealed by less incidence of disease lesion and cell death, and lower bacterial density in leaves (P≤0.01). Furthermore, evening-sampled leaves had higher starch content (0-48 h), glucose content (0 h and 24 h), and fructose content (24 h and 48 h). However, there was no significant difference in sucrose content between two kinds of leaves. In addition, the measurement of three kinds of invertase activities showed that evening-sampled leaves had lower cell wall invertase (CWIN) activity at 0 h and 48 h after inoculation, but significantly (P≤0.05) higher cytoplasmic invertase (CIN) activities at 24 h and 48 h after inoculation than morning-sampled leaves. Notably, there was no significant difference in vacuolar invertase (VIN) activity between two kinds of leaves, Finally, as compared with the morning-sampled leaves, evening-sampled leaves showed significantly (P≤0.05)higher content of free SA and JA, and simultaneously less H₂O₂ accumulation at 48 h after inoculation. In conclusion, as compared with the morning-sampled leaves, evening-sampled leaves showed higher starch and hexose content, CIN activity, but lower CWIN activity. These differences in sugar metabolism may contribute to higher SA and JA content and less H₂O₂ accumulation and cell death in evening-sampled leaves, and ultimatly enhance its resistance to Pst DC3000.