Comparison of the expression of a cold responsive transcript (CLTa) in nine citrus species and Poncirus trifoliata

Trifoliate orange [Poncirus trifoliata (L) Raf] is a cold hardy citrus relative with great potential to be used as a model plant to study the molecular basis of cold acclimation in tree crops. A citrus low temperature responsive gene (CLT) was recently isolated from P. trifoliata by acclimating this plant to -5°C. CLT produces two transcripts in low temperature called CLTa and CLTb. CLTa is expressed specifically when plants are subjected to low-temperatures while CLTb is constitutively expressed.; Other citrus species have varying degrees of resistance to cold and, therefore it is expected that there will be a difference in the molecular response to this stress depending on species. The objective of this research was to study the expression of CLTa in nine citrus species, with varying degrees of sensitivity to cold, compared to the expression in trifoliate orange.; Genomic analysis and RT-PCR were conducted and it was observed that all species studied contained the CLT gene in their genome and expressed equally the constitutive transcript CLTb. However, the expression of the inducible transcript CLTa, was time dependent, with the cold hardy species responding quicker than the cold sensitive.; The expression of CLTa in trifoliate orange acclimated for 12 h was higher than its expression in the cold sensitive Mexican Lime acclimated for 7 days. It is possible that this time-response fashion is controlled at the transcription level by the expression of transcription factors. (Abstract shortened by UMI.)...