Vashisht Ajay Amar, Tuteja Narendra
Plant Molecular Biology, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
J Photochem Photobiol B. 2006 Aug 1;84(2):150-60. doi: 10.1016/j.jphotobiol.2006.02.010. Epub 2006 Apr 19.
Abiotic stresses including various environmental factors adversely affect plant growth and limit agricultural production worldwide. Minimizing these losses is a major area of concern for all countries. Therefore, it is desirable to develop multi-stress tolerant varieties. Salinity, drought, and cold are among the major environmental stresses that greatly influence the growth, development, survival, and yield of plants. UV-B radiation of sunlight, which damages the cellular genomes, is another growth-retarding factor. Several genes are induced under the influence of various abiotic stresses. Among these are DNA repair genes, which are induced in response to the DNA damage. Since the stresses affect the cellular gene expression machinery, it is possible that molecules involved in nucleic acid metabolism including helicases are likely to be affected. The light-driven shifts in redox-potential can also initiate the helicase gene expression. Helicases are ubiquitous enzymes that catalyse the unwinding of energetically stable duplex DNA (DNA helicases) or duplex RNA secondary structures (RNA helicases). Most helicases are members of DEAD-box protein superfamily and play essential roles in basic cellular processes such as DNA replication, repair, recombination, transcription, ribosome biogenesis and translation initiation. Therefore, helicases might be playing an important role in regulating plant growth and development under stress conditions by regulating some stress-induced pathways. There are now few reports on the up-regulation of DEAD-box helicases in response to abiotic stresses. Recently, salinity-stress tolerant tobacco plants have already been raised by overexpressing a helicase gene, which suggests a new pathway to engineer plant stress tolerance [N. Sanan-Mishra, X.H. Pham, S.K. Sopory, N. Tuteja, Pea DNA helicase 45 overexpression in tobacco confers high salinity tolerance without affecting yield. Proc. Natl. Acad. Sci. USA 102 (2005) 509-514]. Presently the exact mechanism of helicase-mediated stress tolerance is not understood. In this review we have described all the reported stress-induced helicases and also discussed the possible mechanisms by which they can provide stress tolerance.
包括各种环境因素在内的非生物胁迫会对植物生长产生不利影响，并限制全球农业生产。尽量减少这些损失是所有国家关注的一个主要领域。因此，培育多胁迫耐受性品种是很有必要的。盐度、干旱和寒冷是严重影响植物生长、发育、存活和产量的主要环境胁迫因素。阳光中的UV - B辐射会损害细胞基因组，是另一个抑制生长的因素。在各种非生物胁迫的影响下，会诱导出几个基因。其中包括DNA修复基因，它们是因DNA损伤而被诱导产生的。由于这些胁迫会影响细胞基因表达机制，参与核酸代谢的分子（包括解旋酶）很可能会受到影响。光驱动的氧化还原电位变化也可以启动解旋酶基因的表达。解旋酶是普遍存在的酶，可催化能量稳定的双链DNA（DNA解旋酶）或双链RNA二级结构（RNA解旋酶）的解旋。大多数解旋酶是DEAD - box蛋白超家族的成员，在DNA复制、修复、重组、转录、核糖体生物合成和翻译起始等基本细胞过程中发挥重要作用。因此，解旋酶可能通过调节一些胁迫诱导途径，在胁迫条件下调节植物生长和发育方面发挥重要作用。目前关于DEAD - box解旋酶响应非生物胁迫而上调的报道较少。最近，通过过表达一个解旋酶基因培育出了耐盐胁迫的烟草植株，这为培育植物胁迫耐受性提供了一条新途径 [N. 萨南 - 米什拉，X.H. 范，S.K. 索波里，N. 图特亚，豌豆DNA解旋酶45在烟草中的过表达赋予高耐盐性且不影响产量。美国国家科学院院刊102 (2005) 509 - 514]。目前尚不清楚解旋酶介导的胁迫耐受性的确切机制。在这篇综述中，我们描述了所有已报道的胁迫诱导解旋酶，并讨论了它们提供胁迫耐受性的可能机制。
