Study the Expression Changes of Pdu-miR319a, Pdu-miR398a-3p and Their Target Genes in Reproductive Tissues of Almond under Cold Stress

Due to the low chilling requirement of almond, this plant encounters yearly with irreparable damages by late spring frost. The introduction of tolerant cultivars using genetic engineering methods, depends on the identification of molecular mechanisms involved in cold stress response. In recent studies the important role of small RNAs especially miRNAs have been confirmed in the response and adaptation of plants to biotic and abiotic stresses. Therefore, based on the sRNA sequencing results of almond, among identified cold-responsive miRNAs, in this study, the expression pattern of Pdu-miR319a and Pdu-miR398a-3p along with their targets were compared between two cold tolerant and sensitive genotypes of almond.

The reproductive tissues of almond (anther and ovary) from H as tolerant genotype and Sh12 as sensitive variety were treated under 0 and -2 ᵒC. After RNA extraction and cDNA synthesis Real Time PCR was performed and expression data were analyzed by 2- ΔΔct method.

MiR319a was identified with a positive regulatory effect in response to both cold stress levels in two genotypes. The downregulation of GAMYB-like was observed in both tissues of H under 0ᵒC and also in the ovary of Sh12 under 0 and -2 ᵒC. The expression of TCP4 was significantly increased in H under both stress levels. MiR398a-3p was detected with a negative regulatory effect in the H but the induction of CTR6 was observed in both tissues under -2ᵒC. In Sh12 the upregulation of miR398a-3p and the downregulation of CTR6 was observed.

Regarding to the differential expression of studied genes between two genotypes, in order to complete the molecular information about their function, it is recommended to examine their expression among other tolerant and sensitive varieties under different cold stress treatments, and followed by their function should be assessed using methods such as over expression, amiRNA technology and target mimicry.