Plasma membrane proteins (PMP3) play a role in cation homoeostasis. The 5flanking sequence ofstress inducible, Avicennia marina PMP3 (AmPMP3prom) was transcriptionally fused to (a) GUS or (b)GFP-AmPMP3 and analyzed in transgenic tobacco. Tissue-histochemical GUS and GFP:AmPMP3 localiza-tion are co-incident under basal and stress conditions. AmPMP3prom directed GUS activity is highest inroots. Basal transcription is conferred by a 388 bp segment upstream of the translation start site. A 463 bpdistal enhancer in the AmPMP3prom confers enhanced expression under salinity in all tissues and alsoresponds to increases in salinity. The effect of a central, stem-specific negative regulatory region is sup-pressed by the distal enhancer. The A. marina rhizosphere encounters dynamic changes in salinity at theinter-tidal interface. The complex, tissue-specific transcriptional responsiveness of AmPMP3 to salinityappears to have evolved in response to these changes. Under salinity, guard cell and phloem-specificexpression of GFP:AmPMP3 is highly enhanced. Mesophyll, trichomes, bundle sheath, parenchymatouscortex and xylem parenchyma also show GFP:AmPMP3 expression. Cis-elements conferring stress, rootand vascular-specific expression are enriched in the AmPMP3 promoter. Pronounced vascular-specificAmPMP3 expression suggests a role in salinity induced Na+transport, storage, and secretion in A. marina.

http://www.sciencedirect.com/science/article/pii/S0168945215000837