| A citrus low temperature responsive gene called CLT was recently identified in the cold hardy citrus relative, Trifoliate orange (Poncirus trifoliata [L.] Raf.) demonstrated notable patterns when expressed during cold acclimation. At room temperature, one transcript was constitutively expressed while another transcript with the same open reading frame was expressed only when the temperature dropped below 10°C. The transcript expressed at low temperature had an additional 98 nucleotides at the 3' untranslated region (3'UTR), which was part of an intron, and was absent in the constitutive transcript. However, keeping the plant for seven days under low temperature, the additional transcripts would be expressed. To determine whether these transcripts are splicing variants produced by the same gene or expressed by additional genes, we screened a bacterial artificial chromosome (BAC) library from P. trifoliata. Thirteen positive clones were identified and after PCR amplification three genes were identified. Two of them had exactly the same sequence, with the exception of the promoter region and the GT repeats (eight GT's and five GT's) at the 3'UTR. The third had an entirely different sequence, but it contained the CLT's ORF and a part of the 3'UTR. |
