Isolation and characterization of an isocitrate lyase gene from senescent leaves of sweet potato (Ipomoea batatas cv. Tainong 57)

Isolation and characterization of an isocitrate lyase gene from senescent leaves of sweet potato (Ipomoea batatas cv. Tainong 57)

2000

A:PS

Sweet potato yellow leaves with disassembled chloroplast thylakoids and remarkable osmiophilic globule accumulation in stroma were used in this study. Using both PCR-based subtractive hybridization and RACE PCR, a 2.1 kb full-length spICL cDNA was cloned. The open reading frame contained 1728 nucleotides (576 amino acids) and exhibited more than 75% sequence identity with plant cotyledon isocitrate lyases of tomato, upland cotton, cucumber, castor bean, rape, soyabean, and loblolly pine. The spICL-encoded protein contained the Leu-169, Lys-170, Pro-171 (LKP) and Thr-210, Lys-211, Lys-212 (TKK) motifs, with a reported substrate binding domain function, as well as a putative peroxisomal targeting signal (PTS) Ala-Arg-Met (ARM) tripeptide at the C-terminus. Its mRNA accumulated exclusively in the senescing and completely yellow leaves, but not in the green leaves, roots, or stems. The sweet potato spICL is the first isocitrate lyase isolated from senescent leaves. The data may provide molecular evidence to support the notion that glyoxylate cycle, a metabolic pathway utilized in cotyledons for postgerminative growth of oilseeds, is also involved in lipid degradation and gluconeogenesis of senescent leaves.

v.157(6):669-676, JOURNAL OF PLANT PHYSIOLOGY

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