Expression of a phosphoenolpyruvate carboxylase promoter from Mesembryanthemum crystallinum is not salt-inducible in mature transgenic tobacco.

The 5' flanking region of a salt-stress-inducible, CAM-specific phosphoenolpyruvate carboxylase (PEPC) gene from the facultative halophyte Mesembryanthemum crystallinum, was fused to the beta-glucuronidase (GUS) reporter gene and introduced into Nicotiana tabacum SR1. The Ppc1 promoter displayed high levels of expression in transgenic tobacco quantitatively and qualitatively similar to a full-length 35S CaMV-GUS construct. Histochemical assays revealed that the full-length Ppc1-GUS fusions expressed GUS activity in all tissues except in root tips. While tobacco is capable of utilizing the Ppc1 cis-acting regulatory regions from M. crystallinum to yield high levels of constitutive expression, this glycophyte fails to direct a stress-inducible pattern of gene expression typical of this promoter in its native, facultative halophytic host.

Regeneration of multiple shoots and plants from Mesembryanthemum crystallinum.

Mesembryanthemum crystallinum plants have been regenerated via organogenesis from hypocotyl, cotyledonary node, and leaf expiants with varying frequencies. The highest regeneration frequencies were obtained from either hypocotyls (23-34%) or cotyledonary nodes (21-41%). Leaf expiants yielded very poor regeneration frequencies (0-11%). Expiants were placed on Murashige and Skoog (MS) media supplemented with 3% sucrose, 0.8% bacto-agar and either, 10.8×10(-6)M NAA and 8.8×10(-6)M BA (MSmsh), 1×10(-5)M BA and 1×10(-6)M IAA, (MS4) or 1×10(-6)M BA and 1×10(-6)M IAA (MS5). Shoot formation frequencies were greater on MS4 and MS5 and lower on MSmsh, however, overall differences of regeneration frequency among media tested were not statistically significant. Regenerated plantlets were rooted on MS medium without growth regulators. Mature, regenerated plants were fertile and exhibited DNA content and ploidy profiles that were identical to wild type plants.