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Abstract

The structure and expression of a novel senescence-associated gene (SPA15) of sweet potato were characterized. The protein coding region of the gene consists of 13 exons encoding 420 amino acids. Apparent homologues of this sweet potato gene are found in a variety of dicot and monocot plants, but not in animals or microorganisms. Examination of the expression patterns of the SPA15 gene in sweet potato reveals that the transcripts of SPA15 are specifically induced in the senescing leaves, and the temporal profile of SPA15 protein accumulation is correlated with that of SPA15 transcripts. Studies on the distribution of SPA15 homologue in rice plants also indicate that SPA15 homologue is up-regulated specifically in senescing rice leaves. Treatment of detached sweet potato leaves with phytohormones including ethylene, methyl jasmonate, salicylic acid and abscisic acid resulted in a high-level induction of SPA15. Immunoelectron microscopic analysis demonstrates that SPA15 is specifically associated with the cell wall. The potential role for SPA15 during leaf senescence is discussed.

Role of ARABIDOPSIS A-FIFTEEN in regulating leaf senescence involves response to reactive oxygen species and is dependent on ETHYLENE INSENSITIVE2

“…SAG12 was used as a senescence marker (Lohman et al , 1994). Therefore, it was confirmed that AAF is also a SAG in Arabidopsis , similar to its orthologues in rice and sweet potato (Yap et al , 2003). However, AAF was also expressed in young leaves (Fig.…”

“…However, SPA15 was detected to associate specifically with the cell wall of various cell types, predominantly in senescent sweet potato leaves, by immunoelectron microscopic analysis (Yap et al , 2003). To test the functionality of the predicted transit peptide in SPA15, a GFP fusion of SPA15 under the control of the CaMV 35S promoter, CaMV35S::SPA15:GFP , was generated for a transient expression assay in Arabidopsis mesophyll protoplasts.…”

“…8C–E). Yap et al (2003) showed that expression of SPA15 was significantly induced by ethylene in detached sweet potato leaves. It is possible that the expression of AAF is induced by ethylene in Arabidopsis .…”

“…A SAG was previously identified in sweet potato ( Ipomoea batatas ) by a differential display approach and it was named SWEET POTATO A15 ( SPA15 ) (Yap et al , 2003). However, the physiological function of SPA15 was not clear.…”

Changes in activities of antioxidant enzymes and their gene expression during leaf development of sweetpotato

“…Two senescence marker genes, spa15 and spg31, in sweetpotato were used as positive controls (Huang et al 2001;Yap et al 2003). As shown in Fig.…”