-

The purpose of this work was to examine changes in expression of cold ¬
inducible genes and frost hardiness as cell responses to combinations of sucrose and low' positive temperatures. Barley calli induced from immature embryos were grown in an MS based medium without agar at 25°C. The cultures were then subcultured into the same medium bu! containing. 0.1 or 30/0 sucrose, and exposed to 6°/2°C (1 0/14h) for either 5 or 10 days. Following frost test, Cold hardiness was determined either by assessment of survival or estimated by electrolyte leakage test (cell damage). Total RNA was extraCted from control as well as treated calli and Northern blotting was performe_ to examine the mRNA levels-of HmGlt4, HmAPlt2,2 and dhn 1. The results showed the effect of low temperature (6"/2°C) in increasing cold hardening. Also, 30/0 sucrose improved the freezing tolerance in both control and cold treated cultures as
compared to 0.1 0/0. This was accompanied by_ accumulation of transcripts from the
tested cold-inducible genes. Also, The enhancement of freezing tolerance and gene
expression," as a result of increase in sucrose concentration (from 0.1 to 30/0) even at
non-inductive temperature (25°C) was much higher than that resulted from changing
growth temperature frol11 25°C to 6°/2°C. Thus, sugar concentration could be the
critical factor during cold-acclimation rather than temperature.