Cloning and properties of a rice gene encoding phenylalanine ammonia-lyase

Abstract

Phenylalanine ammonia-lyase (PAL) genomic sequences were isolated from a rice (Oryza sativa L.) genomic library using a PCR-amplified rice PAL DNA fragment as a probe. There is a small family of PAL genes in the rice genome. The nucleotide sequence of one PAL gene, ZB8, was determined. The ZB8 gene is 4660 bp in length and consists of two exons and one intron. It encodes a polypeptide of 710 amino acids. The transcription start site was 137 bp upstream from the translation initiation site. Rice PAL transcripts accumulated to a high level in stems, with lower levels in roots and leaves. Wounding of leaf tissues induced ZB8 PAL transcripts to a high level. In rice suspension-cultured cells treated with fungal cell wall elicitors, the ZB8 PAL transcript increased within 30 min and reached maximum levels in 1-2 h. The transcription of the ZB8 gene was investigated by fusing its promoter to the reporter gene beta-glucuronidase (GUS) and transforming the construct into rice and tobacco plants, as well as rice suspension-cultured cells. High levels of GUS activity were observed in stems, moderate levels in roots and low levels in leaves of transgenic rice and tobacco plants. Histochemical analysis indicated that in transgenic rice the promoter was active in root apical tips, lateral root initiation sites, and vascular and epidermal tissues of stems and roots. In rice flowers, high GUS activity was observed in floral shoots, receptacles, anthers and filaments, occasionally GUS activity was also detected in lemma and awn tissues. In tobacco flowers, high GUS activity was detected in the pink part of petals. Consistent with the activity of endogenous PAL transcripts, wounding of rice and tobacco leaf tissues induced GUS activity from low basal levels. Tobacco mosaic virus (TMV) infection of tobacco leaves induced GUS activity to a high level. Fungal cell wall elicitors strongly induced GUS activity and GUS transcripts to high levels in transgenic rice suspension-cultured cells. We demonstrated that the promoter of ZB8 gene is both developmentally regulated and stress-inducible.

Transcription profiling identifies candidate genes for secondary cell wall formation and hydroxycinnamoyl-arabinoxylan biosynthesis in the rice internode

“…Monolignol synthesis and hydroxycinnamoylCoA synthesis were expected to be up-regulated in the wild-type whole internode and F71 pith parenchyma, respectively, and the expression profiles of genes in the phenylpropanoid pathway were determined. Although many researchers have studied genes in the phenylpropanoid pathway in rice, in many cases only a subset of these genes were targeted, and not all of the genes in this pathway have been identified (Kawasaki et al 2006; Lee et al 2007Lee et al , 2008Ma 2007;Minami et al 1989;Tobias and Chow 2005;Zhang et al 2006;Zhao et al 2004;Zhu et al 1995). The list of phenylpropanoid pathway genes in rice and the corresponding probe sets was based on all of these studies and a report on Arabidopsis genes by Raes et al (2003) (Table S4).…”

OsWRKY03, a rice transcriptional activator that functions in defense signaling pathway upstream of OsNPR1

“…PAL has been proven to be a key enzyme in pathogen defense and stress response [69,70]. ZB8 is a rice PAL gene and has been shown to be induced under wounding and fungal cell wall elicitor treatment [71]. Peroxidase genes are also a class of protective genes that are induced in plant defense response [5].…”

Bacterial effector modulation of host E3 ligase activity suppresses PAMP-triggered immunity in rice

“…We treated these XopP Xoo -OX cells with a bacterial MAMP PGN. Quantitative RT-PCR indicated that the expression of two defence-related genes, Probenazole1 (PBZ1) 30 and Phenylalanine ammonia-lyase1 (PAL1) 31 , was significantly suppressed in the XopP Xoo -OX cells (Fig. 1g).…”