Kumar Kundan, Mosa Kareem A, Chhikara Sudesh, Musante Craig, White Jason C, Dhankher Om Parkash
Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA, 01003, USA.
Planta. 2014 Jan;239(1):187-98. doi: 10.1007/s00425-013-1969-y. Epub 2013 Oct 20.
Boron (B) toxicity is responsible for low cereal crop production in a number of regions worldwide. In this report, we characterized two rice genes, OsPIP2;4 and OsPIP2;7, for their involvement in B permeability and tolerance. Transcript analysis demonstrated that the expression of OsPIP2;4 and OsPIP2;7 were downregulated in shoots and strongly upregulated in rice roots by high B treatment. Expression of both OsPIP2;4 and OsPIP2;7 in yeast HD9 strain lacking Fps1, ACR3, and Ycf1 resulted in an increased B sensitivity. Furthermore, yeast HD9 strain expressing OsPIP2;4 and OsPIP2;7 accumulated significantly higher B as compared to empty vector control, which suggests their involvement in B transport. Overexpression of OsPIP2;4 and OsPIP2;7 in Arabidopsis imparted higher tolerance under B toxicity. Arabidopsis lines overexpressing OsPIP2;4 and OsPIP2;7 showed significantly higher biomass production and greater root length, however there was no difference in B accumulation in long term uptake assay. Short-term uptake assay using tracer B (¹⁰B) in shoots and roots demonstrated increased ¹⁰B accumulation in Arabidopsis lines expressing OsPIP2;4 and OsPIP2;7, compare to wild type control plants. Efflux assay of B in the roots showed that ¹⁰B was effluxed from the Arabidopsis transgenic plants overexpressing OsPIP2;4 or OsPIP2;7 during the initial 1-h of assay. These data indicate that OsPIP2;4 and OsPIP2;7 are involved in mediating B transport in rice and provide tolerance via efflux of excess B from roots and shoot tissues. These genes will be highly useful in developing B tolerant crops for enhanced yield in the areas affected by high B toxicity.
硼（B）毒性是全球许多地区谷类作物产量低下的原因。在本报告中，我们对两个水稻基因OsPIP2;4和OsPIP2;7进行了表征，以确定它们在硼通透性和耐受性方面的作用。转录分析表明，高硼处理使OsPIP2;4和OsPIP2;7在地上部的表达下调，而在水稻根部强烈上调。在缺乏Fps1、ACR3和Ycf1的酵母HD9菌株中表达OsPIP2;4和OsPIP2;7均导致硼敏感性增加。此外，与空载体对照相比，表达OsPIP2;4和OsPIP2;7的酵母HD9菌株积累的硼显著更高，这表明它们参与硼转运。在拟南芥中过表达OsPIP2;4和OsPIP2;7可使其在硼毒性下具有更高的耐受性。过表达OsPIP2;4和OsPIP2;7的拟南芥株系显示出显著更高的生物量产量和更长的根长，然而在长期吸收试验中硼积累没有差异。使用示踪硼（¹⁰B）对地上部和根部进行的短期吸收试验表明，与野生型对照植物相比，表达OsPIP2;4和OsPIP2;7的拟南芥株系中¹⁰B积累增加。根部硼外流试验表明，在试验的最初1小时内，¹⁰B从过表达OsPIP2;4或OsPIP2;7的拟南芥转基因植物中流出。这些数据表明，OsPIP2;4和OsPIP2;7参与介导水稻中的硼转运，并通过将过量的硼从根和地上部组织中流出提供耐受性。这些基因对于培育耐硼作物以提高受高硼毒性影响地区的产量将非常有用。
