LOCALIZATION OF EXPRESSION OF 3 COLD-INDUCED GENES, BLT101, BLT4.9, AND BLT14, IN DIFFERENT TISSUES OF THE CROWN AND DEVELOPING LEAVES OF COLD-ACCLIMATED CULTIVATED BARLEY

Tissues expressing mRNAs of three cold-induced genes, blt101, blt14, a nd blt4.9, and a control gene, elongation factor 1 alpha, were identif ied in the crown and immature leaves of cultivated barley (Hordeum vul gare L. cv Igri). Hardiness and tissue damage were assessed, blt101 an d blt4.9 mRNAs were not detected in control plants; blt14 was expresse d in control plants but only in the inner layers of the crown cortex. blt101 was expressed in many tissues of cold-acclimated plants but mos t strongly in the vascular-transition zone of the frown; blt14 was exp ressed only in the inner layers of the cortex and in cell layers partl y surrounding Vascular bundles in the vascular-transition zone; expres sion of blt4.9, which codes for a nonspecific lipid-transfer protein, was confined to the epidermis of the leaf and to the epidermis of the older parts of the crown. None of the cold-induced genes was expressed in the tunica, although the control gene was most strongly expressed there. Thus, the molecular aspects of acclimation differed markedly be tween tissues. Damage in the vascular-transition zone of the crown cor related closely with plant survival. Therefore, the strong expression of blt?Ol and blt14 in this zone may indicate a direct role in freezin g tolerance of the crown.