Comparative transcriptome combined with morpho-physiological analyses revealed candidate genes potentially for differential cold tolerance in two contrasting apricot (Prunus armeniaca L.) cultivars

Abstract

We performed a comparative transcriptome combined with morpho-physiological analyses between two differential cold tolerance in two contrasting apricot cultivars. The revealed candidate genes potentially were identified by differential expression analysis. Apricot (Prunus armeniaca L.) is a major (non-wood product) forest tree species that is adversely affected by spring frost. However, the mechanisms regulating gene expression in response to frost under natural conditions remains relatively uncharacterized. In this study, we analyzed the phenotypic, anatomical, physiological and molecular characteristics of pistils from two apricot cultivars that differ regarding cold tolerance under spring frost. A total of 217,142,216 and 218,148,439 clean reads were obtained for the cold-tolerant (‘Weixuan 1’) and the cold-sensitive (‘Longwangmao’) sample libraries, respectively. Moreover, 57,689 unigenes (≥ 200 bp long) were identified, with an N50 of 2468 bp and a mean length of 1038.08 bp. Furthermore, 1116 up-regulated and 428 down-regulated differentially expressed genes (DEGs) were identified in the two apricot cultivars. Thirteen DEGs related to Ca2+ signaling, four DEGs involved in MAPK cascades, and thirty DEGs encoding transcription factors were affected by spring frost. The most significant transcriptome changes induced by spring frost were related to carbohydrate metabolism, amino acid metabolism, lipid metabolism, secondary metabolites, plant hormone signal transduction, and terpenoid metabolism. Notably, bHLH75, GDSL esterase/lipase EXL3, GDSL esterase/lipase LTL1, and peroxidase-66 were more highly expressed in ‘Weixuan 1’ than in ‘Longwangmao’ under 6:00, suggesting these genes may contribute to the cold tolerance of ‘Weixuan 1’. The reliability of our RNA sequencing results was confirmed by quantitative real-time PCR. The data generated in this study may form the basis of future studies on the mechanisms underlying the cold tolerance of apricot under natural field conditions.