Cloning and characterization of leaf senescence up‐regulated genes in sweet potato

Abstract

Genes that are expressed during leaf senescence in sweet potato (Ipomoea batatas, cv. Tainong 57) were identified by the isolation of cDNA fragments with the mRNA differential display method. Eight senescence-associated cDNA clones for mRNAs differentially expressed during leaf senescence were obtained and characterized. Northern blot analysis indicated that all these clones represented genes that are up-regulated during natural leaf senescence. Among them, five cDNA clones have been obtained in full length by screening a senescing leaf cDNA library or by performing rapid amplification of cDNA ends. DNA and protein database searches revealed that clones SPA15 and SPC9 encode proteins of unknown function. The other six clones SPG31, SPC20, SPG27, SPC25, SPC15 and SPC1 showed significant sequence homology to known genes encoding a cysteine proteinase, isocitrate lyase, S-adenosylmethionine decarboxylase, cysteine proteinase inhibitor and metallothionein-like type I protein. The gene expression patterns represented by SPG31, SPG27 and SPA15 were found to be highly specific in senescing leaves. The corresponding transcripts for SPG31, SPG27 and SPA15 were below detectable levels in other organs such as flowers, stems, roots and tubers. The possible physiological roles of these gene products in the leaf senescence process are discussed.

Genome-Wide Identification of Nodule-Specific Transcripts in the Model Legume Medicago truncatula

“…These include TCs that encode proteins similar to: (a) purine permease, a high-affinity transporter for adenine, cytosine, and purine derivatives (Gillissen et al, 2000); (b) plantacyanin, a plant-specific blue copper protein, apparently involved in the defense response (Nersissian et al, 1998); (c) a homolog of an Arabidopsis embryospecific protein, whose cellular function is yet to be understood; (d) B12D protein, a protein known to be accumulated in plants during embryo development, seed maturation, and leaf senescence (Aalen et al, 1994;Huang et al, 2001); (e) remorin, a membrane phosphoprotein, suggested to be involved in intercellular communications (Reymond et al, 1996); (f) 2-on-2 hemoglobin, the higher plant homolog of the "truncated" hemoglobins found in bacteria, protozoa, and algae, which possess unique biochemical properties that are likely distinct from those of other plant hemoglobins (Watts et al, 2001); and (g) calmodulinlike proteins.…”

Response to Plant Hormones of Senescence-related Genes for Cucumis sativus L. in Cotyledon Development

“…Cucumber metallothioneinlike type 3 protein coding SAG 66 (named as CsMTP3) is extremely active in developing cotyledon. Gene expression has been reported in Brassica napus leaves, post-harvest floret of broccoli (Brassica oleraces), and leaves of senescing sweet potato (Imopoea batatas) [5,14,24]. Furthermore, protein coding GhMT3a gene showed strong expression against various external stresses not only to drought, salinity, low temperature, but also to abscisic acid (ABA), ethylene and reactive oxygen species (ROS) in cotton seedlings [40].…”

Molecular investigation of two contrasting genotypes of Medicago truncatula to salt stress using two expressed sequence tag-simple sequence repeat (EST-SSRs) markers

“…Another interest focuses on enzymes like proteinases that are implicated in many cellular reactions involving protein degradation, such as degradation of storage proteins; their action can be inhibited by cysteine proteinase inhibitors, or cystatins superfamily. Expression of the proteinase inhibitor genes is usually limited to specific organs or to particular phases during plant growth: germination (Botella et al, 1996), early leaf senescence (Huang et al, 2001), drought (Waldron et al, 1993) or cold and salt stresses (Pernas et al, 2000;Van der Vyver et al, 2003). Information is still limited about the regulation of these inhibitors in plants and especially in the leguminous M. truncatula and their possible interaction with proteinases under salt stress conditions.…”