郑绍建教授实验室连发两篇重要论文

　　

生物通报道：浙江大学郑绍建教授实验室主要从事植物响应铝毒、缺铁等营养逆境的生理和分子机制的研究。近期其研究组接连发表《Plant Physiology》、《Plant Cell and Environment》文章，获得了两项重要研究进展。

第一篇文章中，研究人员发现植物细胞壁半纤维是结合铝Al的主要组分，并且铝导致的根系伸长受阻与根系半纤维素合成相关基因表达的变化相关。这一研究成果公布在Plant Physiology上。

铝毒是限制酸性土壤作物生长的主要因素。我国酸性土壤遍及南方15个省区，总面积为2030万hm~2，约占全国土地总面积的21％。了解铝毒对于细胞的影响，以及其中的分子机制，有助于选育和通过生物工程手段创建适合酸性铝毒土壤上生长的植物。

细胞壁被认为是铝毒性的主要靶标，但是目前有关铝如何积累，以及相关的机制并不清楚。在这篇文章中，研究人员发现植物细胞壁半纤维是结合铝Al的主要组分，并且铝导致的根系伸长受阻与根系半纤维素合成相关基因表达的变化相关。这项研究首次证明了半纤维是铝积累处，对于研究铝毒这汇总营养逆境的生理和分子机制具有重要意义。

另外一篇文章中，研究人员发现番茄根尖在镉胁迫下释放草酸可有效地降低根尖镉的累积，从而提高其耐镉性。这一研究成果公布在《Plant Cell and Environment》。

重金属镉超标，会对农作物和人体都带来危害，对植物的影响，主要表现在破坏叶绿素，从而降低光合作用，还能使花粉败育，影响植物生长、发育和繁殖。

在这篇文章中，研究人员发现了植物对这种重金属的一种自我保护机制：能释放草酸，有效地降低根尖镉的累积，从而提高其耐镉性。这有助于科学家们了解镉代谢的机制，以及模拟这种机制，增加农作物的耐镉性。

（生物通：万纹）

原文摘要：

Cell wall hemicellulose contributes significantly to Al adsorption and root growth in Arabidopsis

Cell wall (CW) has been recognized as the major target of Al toxicity. However, the components responsible for Al accumulation and the mechanisms of Al-induced CW function disruption are still elusive. The contribution of different CW components (pectin, hemicellulose 1 [HC1], and hemicellulose 2 [HC2]) to adsorb Al and the effect of Al on xylogulcan endotransglucosylase/hydrolyases activity were investigate in Arabidopsis in this study. A fractionation procedure was optimized to effectively extract different CW components, esp. to prevent HC fraction from pectin contamination. When CW materials extracted from Al treated roots (50 μM Al for 24 h) were fractionated, Al content in different CW components revealed that about 75% of CW Al retained in HC1 fraction. Furthermore, a time-dependent kinetic study of different CW components to adsorb Al showed that only when HC1 was removed the amount of Al adsorped was decreased sharply. In vivo localization of xyloglucan endotransglucosylase (XET) activity showed that Al greatly inhibited this enzyme activity within 30 min of exposure, which was concomitant with Al-induced callose deposition in roots. Results from real-time reverse transcription-PCR indicated that three genes may constitute the major contributors to XET activity and the inhibition of XET activity by Al is caused by transcriptional regulation. These results for the first time demonstrated that HC is the major pool for Al accumulation. Furthermore, Al-induced reduction in XET activity could play an important role in Al-induced root growth inhibition.

Cadmium-induced oxalate secretion from root apex is associated with cadmium exclusion and resistance in Lycopersicon esulentum

The mechanisms of heavy metal resistance in plants can be classified into internal tolerance and exclusion mechanisms, but exclusion of heavy metals with the help of organic acids secretion has not been well documented. Here we demonstrated the contribution of oxalate secretion to cadmium (Cd) exclusion and resistance in tomato. Different Cd resistance between two tomato cultivars was evaluated by relative root elongation (RRE) and Cd accumulation. Cultivar ‘Micro-Tom’ showed better growth and lower Cd content in roots than ‘Hezuo903’ at different Cd concentrations not only in short-term hydroponic experiment but also in long-term hydroponic and soil experiments, indicating that the genotypic difference in Cd resistance is related to the exclusion of Cd from roots. ‘Micro-Tom’ had greater ability to secrete oxalate, suggesting that oxalate secretion might contribute to Cd resistance. Cd-induced secretion of oxalate was localized to root apex at which the majority of Cd accumulated. Phenylglyoxal, an anion-channel inhibitor, effectively blocked Cd-induced oxalate secretion and aggravated Cd toxicity while exogenous oxalate supply ameliorated Cd toxicity efficiently. These results indicated that the oxalate secreted from the root apex helps to exclude Cd from entering tomato roots, thus contributes to Cd resistance in the Cd-resistant tomato cultivar.

作者简介：

郑绍建教授

国家自然科学基金杰出青年基金获得者、教育部****特聘教授

1986年本科毕业于原浙江农业大学土壤农业化学系，硕士和博士就读于南京农业大学土壤农业化学系，1991年获博士学位后留校任教，在日本学术振兴会和日本科学技术厅博士后奖学金的资助下，1996-1997和1998-2000年期间二度赴日本进行博士后研究，2000年7月回国到浙江大学环境与资源学院工作，并晋升为教授和博士生导师，2006年起调入生命科学学院植物科学研究所，2007年7月起任植物科学研究所所长，2009年7月起任生命科学学院副院长，是植物学国家重点学科植物生理方向的负责人。

主要从事植物响应铝毒、缺铁等营养逆境的生理和分子机制的研究。围绕逆境条件下植物根系分泌物的合成、代谢、调控及其生理生态功能，细胞壁在抵抗营养逆境中的分子生理机制等方面，深入系统地阐明植物应答营养逆境的机制。迄今已主持国家自然科学基金杰出青年基金项目，重点项目1项和面上项目4项，教育部博士点基金1项，其他省部级项目数项。2002年入选教育部优秀青年教师资源计划项目，同年获第八届高校霍英东优秀青年教师基金。迄今已发表论文60余篇，在Nature，Plant Physiology等国际权威性SCI期刊上发表论文40余篇，其中28篇为通讯作者，被SCI期刊源引用600余次。回国后，已逐步建成了开展植物营养逆境分子生理学研究的平台，以通讯作者陆续在Plant Physiology发表论文5篇。

现为国际权威性植物科学SCI期刊“Annals of Botany″（5-year IF 3.724）的地区编委（Regional Editor)，负责植物矿质营养、土壤肥力、根系功能及其他相关方面论文的送审与裁定,同时负责该期刊在中国的宣传与推广工作。国际权威性土壤科学SCI期刊Plant and Soil( 5-year IF 2.799)的领域编委（Section Editor）。现任中国植物生理学会理事，浙江省植物生理学会副会长，浙江省植物学会理事，中国土壤学会土壤-植物营养专业委员会委员。