Expression analysis of a cold responsive transcript from trifoliate orange by real-time PCR and RT-PCR

Area of Science:

• Plant Molecular Biology
• Plant Physiology
• Citrus Genetics

Background:

• The citrus CLT gene produces two transcripts: CLTb (constitutive) and CLTa (cold-responsive).
• CLTa expression is specifically induced at temperatures below 10°C during citrus acclimation to cold.
• Understanding CLTa's role is crucial for citrus cold hardiness research.

Purpose of the Study:

• To investigate the expression pattern of the CLTa transcript in trifoliate orange during cold acclimation and deacclimation.
• To determine the temperature sensitivity and degradation kinetics of CLTa.
• To assess the influence of ABA and salts on CLTa expression and its presence in different citrus species.

Main Methods:

• Real-time PCR was employed to quantify CLTa transcript levels.
• A standard curve was constructed for accurate transcript concentration determination.
• Expression analysis was performed across various temperatures, acclimation/deacclimation stages, and treatments (ABA, salts).

Main Results:

• CLTa expression initiated at 10°C, peaked after 24 hours at -1°C during acclimation.
• CLTa accumulated at 5°C during gradual deacclimation but rapidly degraded at higher temperatures.
• Abrupt transfer to room temperature caused rapid CLTa degradation; ABA and salt treatments did not induce CLTa.

Conclusions:

• CLTa expression is strictly dependent on low temperatures, playing a key role in citrus cold acclimation.
• The rapid degradation of CLTa upon warming indicates a transient cold-response mechanism.
• CLTa was detected in cold-hardy trifoliate orange and Satsuma mandarin but not in cold-sensitive Mexican lime.