Bonasera Jean M, Kim Jihyun F, Beer Steven V
Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA.
BMC Plant Biol. 2006 Oct 9;6:23. doi: 10.1186/1471-2229-6-23.
In the past decade, much work has been done to dissect the molecular basis of the defence signalling pathway in plants known as Systemic Acquired Resistance (SAR). Most of the work has been carried out in model species such as Arabidopsis, with little attention paid to woody plants. However within the range of species examined, components of the pathway seem to be highly conserved. In this study, we attempted to identify downstream components of the SAR pathway in apple to serve as markers for its activation.
We identified three pathogenesis related (PR) genes from apple, PR-2, PR-5 and PR-8, which are induced in response to inoculation with the apple pathogen, Erwinia amylovora, but they are not induced in young apple shoots by treatment with known elicitors of SAR in herbaceous plants. We also identified three PR-1-like genes from apple, PR-1a, PR-1b and PR-1c, based solely on sequence similarity to known PR-1 genes of model (intensively researched) herbaceous plants. The PR-1-like genes were not induced in response to inoculation with E. amylovora or by treatment with elicitors; however, each showed a distinct pattern of expression.
Four PR genes from apple were partially characterized. PR-1a, PR-2, PR-5 and PR-8 from apple are not markers for SAR in young apple shoots. Two additional PR-1-like genes were identified through in-silico analysis of apple ESTs deposited in GenBank. PR-1a, PR-1b and PR-1c are not involved in defence response or SAR in young apple shoots; this conclusion differs from that reported previously for young apple seedlings.
在过去十年中，人们开展了大量工作来剖析植物中被称为系统获得性抗性（SAR）的防御信号通路的分子基础。大部分工作是在拟南芥等模式物种中进行的，对木本植物关注较少。然而，在所研究的物种范围内，该通路的组成部分似乎高度保守。在本研究中，我们试图鉴定苹果中SAR通路的下游组分，以作为其激活的标记。
我们从苹果中鉴定出三个病程相关（PR）基因，PR - 2、PR - 5和PR - 8，它们在接种苹果病原菌梨火疫病菌后被诱导，但在用草本植物中已知的SAR激发子处理幼嫩苹果枝条时未被诱导。我们还仅基于与模式（深入研究的）草本植物已知PR - 1基因的序列相似性，从苹果中鉴定出三个PR - 1类基因，PR - 1a、PR - 1b和PR - 1c。这些PR - 1类基因在接种梨火疫病菌或用激发子处理后未被诱导；然而，每个基因都显示出独特的表达模式。
对来自苹果的四个PR基因进行了部分表征。苹果中的PR - 1a、PR - 2、PR - 5和PR - 8不是幼嫩苹果枝条中SAR的标记。通过对GenBank中保存的苹果EST进行电子分析，又鉴定出另外两个PR - 1类基因。PR - 1a、PR - 1b和PR - 1c不参与幼嫩苹果枝条的防御反应或SAR；这一结论与先前关于苹果幼苗的报道不同。
