Specificity of a promoter from the rice tungro bacilliform virus for expression in phloem tissues

Abstract

The major promoter region for the transcription of the genome of rice tungro bacilliform virus (RTBV), a newly described badnavirus, has been identified. Fragments of the RTBV genome upstream of the site of transcription initiation were isolated and tested for promoter activity using a beta-glucuronidase receptor gene (gusA). Assays of transient gusA expression were performed following introduction of the chimeric gene into protoplasts via electroporation. The chimeric RTBV-promoter: gusA gene was more active in rice protoplasts than in maize or tobacco protoplasts, but was weaker than gusA controlled by an enhanced 35S promoter from cauliflower mosaic virus. Analysis of gusA gene expression following introduction of chimeric reporter genes into intact leaves via micro-projectile bombardment indicated that the GUS activity is present primarily in vascular tissues. Transgenic rice plants carrying the chimeric gusA gene had GUS activity only in the phloem of the vascular bundles in the leaf. Tissue printing studies demonstrated that RTBV accumulates in the vascular bundles of infected rice leaves. The results of our study indicate that phloem-specific expression from the RTBV promoter is an intrinsic property of the viral promoter.

Overexpression of a NAC transcription factor delays leaf senescence and increases grain nitrogen concentration in wheat

“…1993) was to achieve leaf‐targeted expression; the localisation was confirmed in RTBV promoter GUS studies (unpublished). As found in other expression studies, expression of TaNAC‐S in overexpressing lines and control plants was higher in leaf 2 than in the flag leaf (compare Figs 2, 3 and 5).…”

“…After sequencing, the wheat NAC‐S DNA fragment was inserted between the rice tungro bacilliform virus (RTBV) promoter (Bhattacharyya‐Pakrasi et al . 1993) and the 35S termination signal into a modified pBract302 plasmid, in which the ubiquitin promoter‐nos terminator cassette was replaced by the RTBV‐promoter‐TaNAC‐S‐35S‐terminator construct. The plasmid contained the NPT1 kanamycin resistance gene for selection of bacteria and the BAR gene conferring phosphinothricin resistance under control of a ubiquitin promoter to allow for plant selection.…”

RF2b, a rice bZIP transcription activator, interacts with RF2a and is involved in symptom development of rice tungro disease

“…Many plant DNA viruses, including rice tungro bacilliform virus (RTBV), coconut foliar decay virus, and commelina yellow mottle virus, accumulate specifically in phloem tissues, and the expression of their promoters is restricted to vascular tissues in plants (4)(5)(6)(7)(8). Moreover, a number of plant genes that are specifically expressed in vascular tissues have been isolated, including pal2 (9), 4cl (10), PtCesA (11), AtARP2 (12), sh-1 (13), and grp 1.8 (14).…”

Transcriptional Activation of the Rice Tungro Bacilliform Virus Gene Is Critically Dependent on an Activator Element Located Immediately Upstream of the TATA Box

“…RTBV has a circular, double-stranded DNA genome of 8 kilobase pairs from which the terminally redundant pregenomic transcript is produced (19,20,24). A single promoter from the virus genome was isolated, and phloem-specific activity was observed in transgenic rice plants (25), suggesting that the promoter can account for the tissue-specific localization of this virus. The RTBV promoter has been analyzed in both transformed rice plants (26 -28) and transfected rice protoplasts (29,30).…”