Rice phenylalanine ammonia-lyase gene OsPAL4 is associated with broad spectrum disease resistance

Abstract

Most agronomically important traits, including resistance against pathogens, are governed by quantitative trait loci (QTL). QTL-mediated resistance shows promise of being effective and long-lasting against diverse pathogens. Identification of genes controlling QTL-based disease resistance contributes to breeding for cultivars that exhibit high and stable resistance. Several defense response genes have been successfully used as good predictors and contributors to QTL-based resistance against several devastating rice diseases. In this study, we identified and characterized a rice (Oryza sativa) mutant line containing a 750 bp deletion in the second exon of OsPAL4, a member of the phenylalanine ammonia-lyase gene family. OsPAL4 clusters with three additional OsPAL genes that co-localize with QTL for bacterial blight and sheath blight disease resistance on rice chromosome 2. Self-pollination of heterozygous ospal4 mutant lines produced no homozygous progeny, suggesting that homozygosity for the mutation is lethal. The heterozygous ospal4 mutant line exhibited increased susceptibility to three distinct rice diseases, bacterial blight, sheath blight, and rice blast. Mutation of OsPAL4 increased expression of the OsPAL2 gene and decreased the expression of the unlinked OsPAL6 gene. OsPAL2 function is not redundant because the changes in expression did not compensate for loss of disease resistance. OsPAL6 co-localizes with a QTL for rice blast resistance, and is down-regulated in the ospal4 mutant line; this may explain enhanced susceptibility to Magnoporthe oryzae. Overall, these results suggest that OsPAL4 and possibly OsPAL6 are key contributors to resistance governed by QTL and are potential breeding targets for improved broad-spectrum disease resistance in rice.

Genome-wide association mapping for resistance to leaf rust, stripe rust and tan spot in wheat reveals potential candidate genes

“…Phenylalanine ammonia lyase (EC 4.3.1.24) is a key enzyme in the phenylpropanoid pathway of higher plants involved in the production of several compounds like lignins, coumarins and flavonoids that are related to plant defense (La Camera et al 2004). Several studies have reported the induction of the PAL gene in response to fungal elicitors and its association with enhanced fungal defense (Pellegrini et al 1994; Shadle et al 2003; Tonnessen et al 2015). Interestingly, the wheat PAL gene had highly similar orthologs in several other plants indicating that it is conserved across species as observed by Rawal et al (2013).…”

“…Plant defensins are cysteine-rich peptides involved in plant innate immunity that are generally active against a broad spectrum of fungal pathogens and other microbes (Broekaert et al 1995; de Carvalho and Gomes 2009). While the PAL gene has been discussed earlier, Tonnessen et al (2015) reported a rice PAL gene ( OsPAL4 ) that was associated with broad spectrum disease resistance. Finally, the ABCG transporter family (also pleiotropic drug resistance family) members are also known to be involved in plant defense (Stukkens et al 2005; Stein et al 2006; Krattinger et al 2009).…”

Transcriptome Analysis Highlights Defense and Signaling Pathways Mediated by Rice pi21 Gene with Partial Resistance to Magnaporthe oryzae

“…PAL is also involved in the synthesis of phytoalexins and lignin to prevent cell wall penetration by the pathogen. Tonnessen et al (2015) reported that OsPAL4 and possibly OsPAL6 were key contributors to resistance governed by QTL and were potential breeding targets for improved broad-spectrum disease resistance in rice. The expression of PAL6 was up-regulated in the Pi21 -RNAi line relative to Nip as early as 24 hpi.…”

Transcriptomic and histological responses of African rice (Oryza glaberrima) to Meloidogyne graminicola provide new insights into root-knot nematode resistance in monocots

“…Specifically, an earlier (2 dpi) and stronger (6-to 8-fold) activation of OsPAL4 and OsPAL6 was observed. OsPAL4 and to a lesser extent OsPAL6 were shown to be key elements in resistance to several bacterial and fungal diseases governed by QTL (Tonnessen et al, 2015). Inhibition of PAL activity by AOPP application to TOG5681 led to increased gall formation, although this inhibition could not fully restore susceptibility.…”