低氧胁迫下不同耐性苹果砧木呼吸代谢的差异应答机理

Apple (Malus × domestica Borkh) is one of the most economically important fruits worldwide. But apple tree frequently encounters hypoxia stress mainly due to soil waterlogging, soil compaction, or poor soil drainage, causing to yellowing leaf, declined fruit yield and quality in some region. In this study, two apple rootstock (M. hupehensis Rehd and M. toringoides Hughes) differing in hypoxia tolerance will be treated with hydroponics hypoxia to study the variation characteristics of respiration pathways, energy and enzyme activity related to respiratory metabolism, and to elucidate the relationship between variation characteristics and hypoxia tolerance of apple rootstock; The cDNA coding sequence of alcohol dehydrogenase (ADH1), pyruvate decarboxylase (PDC1), lactate dehydrogenase (LDH1) and Alanine aminotransferase (AlaAT1) genes will be amplified by RT-PCR on base of four pairs of specificities primers designed according to the conservative sequence of ADH1, PDC1, LDH1 and AlaAT1and rapid-amplification of cDNA ends (RACE), to analyze the expressions of ADH1, PDC1, LDH1 and AlaAT1 with semi-quantitative RT-PCR as well as the time correspondence of enzyme activities of ADH1, PDC1, LDH1 and AlaAT1gene, and to clarify the role of key genes of respiratory metabolism in response to hypoxia stress. The aims are to provide a theoretical basis for elucidating the response mechanism of respiration metabolism of apple rootstock under hypoxia stress and cultivating high-quality and yield apple.

针对部分地区苹果树常因土壤雨涝积水、排灌不当、土壤质地紧实等造成根际低氧，导致苹果树叶片黄化、脱落，果实产量和品质下降的问题，本项目以根际低氧耐性具有明显差异的苹果砧木平邑甜茶和变叶海棠为试材，采用水培低氧处理的方法，研究不同耐性苹果砧木根系呼吸代谢途径、能量及呼吸代谢相关酶活性的变化特征，探明根系呼吸代谢的变化规律与苹果砧木根际低氧耐性的关系；采用同源序列和RACE技术克隆呼吸代谢关键酶基因ADH1、PDC1、LDH1和AlaAT1的 cDNA部分编码区，用RT-PCR的分析低氧胁迫下不同耐性苹果砧木根系ADH1、PDC1、LDH1和AlaAT1的表达特性差异，并分析其酶活性动态变化特征的差异，明确呼吸代谢其关键基因在苹果砧木应答低氧胁迫中的作用，为全面阐明低氧胁迫下苹果砧木根系呼吸代谢的应答机制及优质高产苹果栽培提供理论依据。

苹果（Malus domestica Borkh）是世界上重要的栽培果树之一，但在实际生产中，经常因淹水、排灌不利、土壤质地紧实和机械操作等原因造成苹果树根际缺氧，引起苹果树叶片黄化、脱落，导致树体衰弱，果实产量和品质下降。严重时造成多年生长受阻，甚至整株死亡，这已成为目前苹果生产中亟待解决的问题。本项目以根际低氧耐性具有明显差异的苹果砧木为试材。利用图像分析软件WinRHIZO和高效液相色谱，研究了低氧胁迫下苹果砧木根系根构型、呼吸代谢能量和相关酶活性动态变化特征及其与低氧耐性的关系，研究表明低氧胁迫下，苹果根构型和根系活力的变化与低氧耐性有关，耐低氧苹果砧木平邑甜茶能保持较好的根系形态和较高的根系活力。同时，低氧胁迫下苹果砧木幼苗根系中苹果酸脱氢酶（MDH）活性显著降低，同时丙酮酸脱羧酶（PDC）、乙醇脱氢酶（ADH）和乳酸脱氢酶（LDH）活性先升后降，揭示了低氧胁迫下，苹果砧木幼苗根系TCAC受阻，电子呼吸链的末端氧化能力下降，根系有氧呼吸代谢受到抑制，耐低氧性强的平邑甜茶幼苗根系中有氧呼吸酶活性下降幅度较小而无氧呼吸酶活性的上升幅度较大，增强了平邑甜茶的抗性。运用RT-PCR扩增到ADH1基因的部分cDNA序列，并对呼吸代谢相关基因进行了序列分析及基因特性的研究，进一步验证了呼吸代谢关键酶基因在低氧胁迫下的作用机制。该项目的实施为深入、系统揭示苹果砧木耐低氧的分子机理奠定了基础，进而为我国苹果抗性资源挖掘利用和抗性育种提供理论依据和指导。