|Keremane, Sravya - UCLA|
|Ramadugu, Chandrika - BOTANY & PLANT SCI-UCR|
|Roose, Mikeal - BOTANY & PLANT SCI-UCR|
Submitted to: Plant and Animal Genome Conference
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2008
Publication Date: N/A
Technical Abstract: Citrus cultivars show a wide range of tolerance to cold temperatures. Lemons and limes are known to be sensitive to cold while certain mandarins and trifoliate oranges can endure severe winters. To understand the mechanism of cold tolerance in citrus, we selected three known cold-sensitive and three cold-tolerant cultivars and studied expression of genes with putative roles in cold tolerance demonstrated in other well studied plant systems. The three genes selected are: ABF3 (abscisic acid-binding factor 3), CLTa (citrus low temperature gene) and a transcription factor ICE I (inducer of CBF expression). Potted plants were acclimated to cold by incubation at 6o C for 48 hours, and samples were collected for RNA extraction. The cDNA samples were analyzed by using SYBR green qPCR to detect expression levels of the three selected genes and a house-keeping gene, malate dehydrogenase. CLTa gene expression increased only in cold-tolerant trifoliate orange. An increase in ICE I gene transcript was observed in the cold-sensitive Mexican lime, cold-tolerant sour orange and trifoliate orange. Expression of ABF3 gene was shown to be up-regulated in cold-tolerant citrus but not in either cold-sensitive citrus varieties or in a related cold-tolerant genus, Poncirus. The results suggest that two different mechanisms of cold tolerance may be present in the two genera, Citrus and Poncirus. The study suggests a major role for ABF3 gene expression in conferring cold tolerance in citrus.