Institut des Sciences du Végétal, CNRS, Gif-sur-Yvette 91198, France.
Plant Cell Environ. 2013 Apr;36(4):804-17. doi: 10.1111/pce.12016. Epub 2012 Oct 24.
Cadmium (Cd) is highly toxic to plants causing growth reduction and chlorosis. It binds thiols and competes with essential transition metals. It affects major biochemical processes such as photosynthesis and the redox balance, but the connection between cadmium effects at the biochemical level and its deleterious effect on growth has seldom been established. In this study, two Cd hypersensitive mutants, cad1-3 impaired in phytochelatin synthase (PCS1), and nramp3nramp4 impaired in release of vacuolar metal stores, have been compared. The analysis combines genetics with measurements of photosynthetic and antioxidant functions. Loss of AtNRAMP3 and AtNRAMP4 function or of PCS1 function leads to comparable Cd sensitivity. Root Cd hypersensitivities conferred by cad1-3 and nramp3nramp4 are cumulative. The two mutants contrast in their tolerance to oxidative stress. In nramp3nramp4, the photosynthetic apparatus is severely affected by Cd, whereas it is much less affected in cad1-3. In agreement with chloroplast being a prime target for Cd toxicity in nramp3nramp4, the Cd hypersensitivity of this mutant is alleviated in the dark. The Cd hypersensitivity of nramp3nramp4 mutant highlights the critical role of vacuolar metal stores to supply essential metals to plastids and maintain photosynthetic function under Cd and oxidative stresses.
镉（Cd）对植物有高度毒性，会导致生长减少和黄化。它与硫醇结合并与必需的过渡金属竞争。它影响主要的生化过程，如光合作用和氧化还原平衡，但镉在生化水平上的作用与其对生长的有害影响之间的联系很少被建立。在这项研究中，比较了两个镉超敏突变体，即 phytochelatin synthase（PCS1）缺陷的 cad1-3 和液泡金属储存释放缺陷的 nramp3nramp4。该分析将遗传学与光合作用和抗氧化功能的测量相结合。AtNRAMP3 和 AtNRAMP4 功能丧失或 PCS1 功能丧失导致可比的 Cd 敏感性。由 cad1-3 和 nramp3nramp4 赋予的根 Cd 超敏性是累积的。这两个突变体在对氧化应激的耐受性方面形成对比。在 nramp3nramp4 中，光合作用器受到 Cd 的严重影响，而在 cad1-3 中则受影响较小。与叶绿体是 nramp3nramp4 中 Cd 毒性的主要靶标一致，该突变体在黑暗中的 Cd 超敏性得到缓解。nramp3nramp4 突变体的 Cd 超敏性突出了液泡金属储存对供应必需金属到质体和维持光合作用功能的关键作用，无论是在 Cd 存在还是在氧化应激下。
