900 Eur J Plant Pathol (2012)133:899-910 known to attack over 250 plant species (O'Bannon populations of Globodera pallida and identified a cel- 1977).R.similis is a migratory endoparasite that lulase and an important pathogenicity factor invades the roots and feeds on the cytoplasm of Meanwhile,several parasite-related genes from cortex cells.As a result,the roots will blacken and Meloidogyne incognita were detected by SSH (Huang die which results in a reduction of plant growth et al.2004).Although mining differentially expressed and development.This destruction of crops leads genes in PPNs is not very difficult,it is crucial to to severe economic losses and consequently,many understand gene function involved in pathogenesis and countries have entered it on the list of quarantine regulation pattems.RNA interference (RNAi)is an plant pests (Cotton and Van Riel 1993;Smith and RNA-dependent gene silencing process in which the Charles 1998). guide strand(small interference RNA,siRNA)from Nematicides have been used as one of many inte short double-stranded RNA (dsRNA)molecules are grated approaches to control plant-parasitic nematodes incorporated into the RNA-induced silencing complex (PPNs).As concems have arisen over the environmen (RISC)to bind to specific mRNA molecules (target tal implications associated with over-using of some mRNA).siRNAs prevent target mRNAs from being translated into protein by either degrac ding target n use mRN om completely trans it yield loss ha Ihus,a ating the mRN. to seek additional app for PPNs contro n recent year molecular bio ing approa trol hav et a we ting diff ath 2000.Ma app che s to i 2004: PCR (R supp iRNA displa (RSDD p y app ole K Sher SSH has the d tiall 1999)SSH ad 1002. sitivity low of fals 2002 tal.2007 d infection in the plan ince more than 100 differ one ssH (vor t al B-1.4-endoglucanase (EGases)also known as cel 1997).Grenier et al.(2002) d SSH to and ie differentially pressed genes betw en two A classified as a fifth glycosy Springerknown to attack over 250 plant species (O'Bannon 1977). R. similis is a migratory endoparasite that invades the roots and feeds on the cytoplasm of cortex cells. As a result, the roots will blacken and die which results in a reduction of plant growth and development. This destruction of crops leads to severe economic losses and consequently, many countries have entered it on the list of quarantine plant pests (Cotton and Van Riel 1993; Smith and Charles 1998). Nematicides have been used as one of many inte￾grated approaches to control plant-parasitic nematodes (PPNs). As concerns have arisen over the environmen￾tal implications associated with over-using of some nematicides, many nematicides have been decreased in use. As a result, shortcomings in our ability to successfully limit yield loss have occurred. Thus, an effort to seek additional approaches for PPNs control is imperative. In recent years, molecular biology and genetic en￾gineering approaches to solve the problem of PPNs control have been developed quickly. In order to have more appropriate biological controls, understanding the molecular mechanisms involved in pathogenicity by mining pathogenicity genes has become extremely important (Chen et al. 2005). It is an effective method to screen for pathogenicity genes by comparing gene expression profiles between different populations of a species exhibiting different levels of pathogenicity on host species. There are a series of approaches to iden￾tify differentially expressed genes, such as mRNA differential display reverse transcription PCR, repre￾sentational difference analysis (RDA), suppression subtractive hybridization (SSH), and reciprocal sub￾traction differential RNA display (RSDD). Of those approaches, SSH has been extensively applied in mo￾lecular genetics and molecular biology (Kuang and Ashorn 1993; Tchernitsa et al. 1999; Shen and Liu 2004). SSH has super sensitivity to recognize the differen￾tially expressed genes in low expression abundance (Diatchenko et al. 1999). SSH advantages include high sensitivity, low occurrence of false positives, high effi￾ciency, and low cost. Commonly, SSH is better than other approaches to detect differentially expressed genes, since more than 100 differentially expressed genes can be enriched in one SSH (von Stein et al. 1997). Grenier et al. (2002) used SSH to investigate differentially expressed genes between two different populations of Globodera pallida and identified a cel￾lulase and an important pathogenicity factor. Meanwhile, several parasite-related genes from Meloidogyne incognita were detected by SSH (Huang et al. 2004). Although mining differentially expressed genes in PPNs is not very difficult, it is crucial to understand gene function involved in pathogenesis and regulation patterns. RNA interference (RNAi) is an RNA-dependent gene silencing process in which the guide strand (small interference RNA, siRNA) from short double-stranded RNA (dsRNA) molecules are incorporated into the RNA-induced silencing complex (RISC) to bind to specific mRNA molecules (target mRNA). siRNAs prevent target mRNAs from being translated into protein by either degrading target mRNAs or inhibiting ribosomes from completely trans￾lating the mRNA. RNAi has been found in many eukar￾yotes including animals and plants. RNAi was initially discovered and developed to application on potato (Kawchuk et al. 1991) and Caenorhabditus elegans (Guo and Kemphues 1995; Fire et al. 1998). RNAi can be used as a simple and effective alternative gene￾knockout tool to obtain function-less or function-loss mutants, because of its high sequence-specificity and effective interference activity. Meanwhile, with its sim￾ple operation, short cycle and low cost, it has become an extremely important tool and most popular research topic in the fields of gene identification, genetic analy￾sis, gene function, gene therapy and genomics (Barstead 2001; Kamath et al. 2000; Maine 2001; Cheng et al. 2003; Rangasamy et al. 2004; Tijsterman et al. 2004). Although it is difficult to study gene function of PPNs by constructing mutants because PPNs are obligatory parasites and do not grow in artificial culture medium; with the advantage above, RNAi could be used for screening mutants, identifying gene function, or control of PPNs (Bakhetia et al. 2007). However, little research has been carried out on the pathogenicity genes of PPNs, and their functions; and, so far, research has also concentrated on the sedentary endoparasitism nemato￾des, such as Meloidogyne sp., Heterodera sp. and Globodera sp. (Goddijn et al. 1993; Brindley et al. 1997; Vercauteren et al. 2002; Shingles et al. 2007). The molecular mechanism of parasitic-related-gene-me￾diated infection in the plant host-parasite interaction is still unclear. β-1, 4-endoglucanase (EGases), also known as cel￾lulase, functions in degrading plant cellulose and is classified as a fifth glycosyl hydrolase family 900 Eur J Plant Pathol (2012) 133:899–910