Genome-wide identification of citrus ATP-citrate lyase genes and their transcript analysis in fruits reveals their possible role in citrate utilization

Abstract

ATP-citrate lyase (ACL, EC4.1.3.8) catalyzes citrate to oxaloacetate and acetyl-CoA in the cell cytosol, and has important roles in normal plant growth and in the biosynthesis of some secondary metabolites. We identified three ACL genes, CitACLα1, CitACLα2, and CitACLβ1, in the citrus genome database. Both CitACLα1 and CitACLα2 encode putative ACL α subunits with 82.5 % amino acid identity, whereas CitACLβ1 encodes a putative ACL β subunit. Gene structure analysis showed that CitACLα1 and CitACLα2 had 12 exons and 11 introns, and CitACLβ1 had 16 exons and 15 introns. CitACLα1 and CitACLβ1 were predominantly expressed in flower, and CitACLα2 was predominantly expressed in stem and fibrous roots. As fruits ripen, the transcript levels of CitACLα1, CitACLβ1, and/or CitACLα2 in cultivars 'Niuher' and 'Owari' increased, accompanied by significant decreases in citrate content, while their transcript levels decreased significantly in 'Egan No. 1' and 'Iyokan', although citrate content also decreased. In 'HB pummelo', in which acid content increased as fruit ripened, and in acid-free pummelo, transcript levels of CitACLα2, CitACLβ1, and/or CitACLα1 increased. Moreover, mild drought stress and ABA treatment significantly increased citrate contents in fruits. Transcript levels of the three genes were significantly reduced by mild drought stress, and the transcript level of only CitACLβ1 was significantly reduced by ABA treatment. Taken together, these data indicate that the effects of ACL on citrate use during fruit ripening depends on the cultivar, and the reduction in ACL gene expression may be attributed to citrate increases under mild drought stress or ABA treatment.

Earlier Degraded Tapetum1 (EDT1) Encodes an ATP-Citrate Lyase Required for Tapetum Programmed Cell Death

“…These results reveal the importance and irreplaceability of cytosolic acetyl-CoA. In a previous report, significantly increased citrate contents under mild drought stress or abscisic acid treatment in fruits can reduce ACL gene expression (Hu et al, 2015). Therefore, ACLs may also participate in other unknown regulatory networks.…”

“…In plants, ACL is a cytoplasmic heterologous protein consisting of two subunits (ACLA and ACLB), probably in an A 4 B 4 configuration (Fatland et al, 2002). ACLA and ACLB are encoded by three and two genes, respectively, in Arabidopsis (Fatland et al, 2002;Hu et al, 2015). Previous study has shown that plants with reduced ACL activity achieved using antisense RNA technology have a complex, bonsai phenotype coupled with reduced accumulation of cuticular wax and excessive accumulation of starch and anthocyanin (Fatland et al, 2005).…”

Functional and Integrative Analysis of the Proteomic Profile of Radish Root under Pb Exposure

“…Beta-glucosidase catalyzes the hydrolysis of the glycosidic and release of glucose, which then entry into the glycolysis process. ATP-citrate lyase (ACL, EC4.1.3.8) is a key enzyme involved in TCA cycle, which catalyzes the cleavage of citrate to yield acetyl CoA, oxaloacetate, ADP, and orthophosphate, and the ACL gene was found to be induced under various stresses including low temperature and drought stimulus (Hu et al, 2015). Pyruvate dehydrogenase could exert a key role in linking the glycolysis to the TCA cycle by catalyzing the formation of an acetyl-CoA from pyruvate (Vuoristo et al, 2015), which is a vital rate-limiting step reaction that determines the rate and efficiency of TCA cycle.…”

OsACL‐A2 negatively regulates cell death and disease resistance in rice

“…In Arabidopsis , ACL is required for normal growth and development, and its overexpression activated the wax, cutin and rubber biosynthetic pathways (Fatland et al ., ; Xing et al ., ). In animals, ACL comprises one polypeptide, whereas in plants, it is composed of two distinct subunits, subunit A and subunit B (Hu et al ., ). However, neither phenotypes caused by mutations in ACL gene have been reported in plants nor the gene for ACL has been isolated in rice so far.…”