Identification of the CaFAB2 Gene Family in Coffea arabica and Its Potential Role in Seed Fatty Acid Synthesis
The quality of Coffea arabica beans is the primary objective of breeding new varieties of C.arabica with high quality,among these,the aroma of coffee bean is the key factor to evaluate the quality of C.arabica bean,and fatty acid is one of the precursors to form volatile aroma components of C.arabica bean.Stearoyl-ACP desaturase(FAB)is an essential enzyme involved in unsaturated fatty acid synthesis in plants,and its desaturation function significantly influences the proportion and unsaturation level of fatty acids.Through Blast comparison analysis,4 members of the CaFAB2 gene family within the C.arabica genome were identified in this study.Further investigation illuminated that these 4 CaFAB2 genes consisted of 381～415 amino acids with molecular weights ranging from 43 936.6 to 47 693.4 D.Besides,these 4 genes also had isoelectric points greater than 7 and exhibited hydrophilic characteristics with instability indices from 29.55 to 42.67 but less than 100 fat index values.And the total average coefficients were all negative,so they were hydrophilic proteins.The proteins of 4 CaFAB2 genes were localized in chloroplasts.Through gene family analysis,it was found that the conserved motif of the CaFAB2 gene family was identical to that of the FAB2 gene family of Arabidopsis thaliana,and the distribution position was highly similar,with the domain PLN00179.Additionally,it was observed that 2 offspring genes corresponded to 1 parental gene between C.eugenoedes and Coffea canephora regarding the presence of CaFAB2 genes in the genome structure of C.arabica.Furthermore,the fatty acid contents were mainly composed of linoleic acid,palmitic acid,oleic acid,and stearic acid during 4 developmental stages of C.arabica seeds,and these 4 compounds indicated the same trend characterized by initial decrease followed by gradual increase.The transcriptome sequencing and real-time fluorescence quantitative PCR analyse revealed a positive correlation between CaFAB2.3 and oleic acid synthesis,while the CaFAB2.1 and CaFAB2.3 primarily participated in early palmitic acid synthesis in the 4 developmental stages of C.arabica seeds.This study provides a theoretical foundation for further investigation on variation tendency and biosynthesis of fatty acids in C.arabica,and offered novel insights into the identification and regulatory mechanisms of CaFAB2 genes in C.arabica.
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