Modulation of eIF5A1 expression alters xylem abundance in Arabidopsis thaliana

Abstract

Eukaryotic translation initiation factor 5A (eIF5A) is thought to facilitate protein synthesis by participating in the nuclear export of specific mRNAs. In Arabidopsis, there are three isoforms of eIF5A. One of them, AteIF5A1, has been shown to be expressed in vascular tissue, specifically developing vessel members, using GUS as a reporter. In order to determine whether AteIF5A1 plays a role in xylem formation, its full-length cDNA was constitutively over-expressed in transgenic Arabidopsis plants. Microscopic analysis revealed that the cross-sectional area of the xylem in the main inflorescence stems of transgenic plants was 1.9-fold higher than those of corresponding inflorescence stems of wild-type plants. In wild-type stems, the primary xylem typically comprised six cell layers and was approximately 105 mum thick, but increased to 9-11 cell layers, 140-155 mum thick, in transgenic stems. Similarly, the secondary xylem increased from six cell layers, approximately 70 mum thick, in control stems to approximately 9 cell layers, 95-105 mum thick, in transgenic stems. Moreover, constitutive down-regulation of AteIF5A1 using antisense technology resulted in the major suppression of xylem formation compared with control plants, and the antisense transgenic plants were also stunted. These data collectively indicate that eIF5A1 plays a role in xylogenesis.

Eukaryotic Translation Initiation Factor 5A Is Involved in Pathogen-Induced Cell Death and Development of Disease Symptoms in Arabidopsis

“…There are three eIF5A gene family members in the Arabidopsis genome: AteIF5A-1 (At1g13950), AteIF5A-2 (At1g26630), and AteIF5A-3 (At1g69410). Antisera were raised against a unique synthetic peptide for each of the three isoforms (Liu et al, 2008). The peptides were synthesized in the laboratory of Dr. G. Lajoie (University of Western Ontario).…”

“…The antibodies were generated against synthetic peptides corresponding to small domains in the C termini of the AteIF5A proteins that exhibit sequence diversity (Liu et al, 2008), and they proved to be isoform specific (Fig. 1A).…”

TheArabidopsisEukaryotic Translation Initiation Factor eIF5A-2 Regulates Root Protoxylem Development by Modulating Cytokinin Signaling

“…In Arabidopsis, eIF5A proteins, including FBR12, have been associated with diverse physiological and pathological processes, including leaf senescence, fruit ripening, stem xylem development, the stress response, and the hypersensitive response (Wang et al, 2001(Wang et al, , 2005Feng et al, 2007;Hopkins et al, 2008;Liu et al, 2008b;Ma et al, 2010). The fbr12 mutant was originally identified as an anti-cell-death mutant (Feng et al, 2007), and the discovery made in this study identifies FBR12/eIF5A-2 as a key regulator of root protoxylem development by modulating cytokinin signaling, thus adding a component in the framework of cytokinin signaling and cytokinin-regulated protoxylem development.…”

“…Mutations in eIF5A-2 cause severe defects in plant growth and development and eventually seedling lethality (Feng et al, 2007). In addition, eIF5A genes regulate stress responses, programmed cell death, stem xylem development, and leaf senescence (Thompson et al, 2004;Feng et al, 2007;Hopkins et al, 2008;Liu et al, 2008b;Ma et al, 2010). In particular, Arabidopsis eIF5A-1 and FBR12/eIF5A-2 genes affect stem xylem development (Feng et al, 2007;Liu et al, 2008b).…”

“…In addition, eIF5A genes regulate stress responses, programmed cell death, stem xylem development, and leaf senescence (Thompson et al, 2004;Feng et al, 2007;Hopkins et al, 2008;Liu et al, 2008b;Ma et al, 2010). In particular, Arabidopsis eIF5A-1 and FBR12/eIF5A-2 genes affect stem xylem development (Feng et al, 2007;Liu et al, 2008b). Moreover, a pumpkin (Cucurbita maxima) eIF5A occurs in the phloem sap and interacts with phloem proteins, implying a possible role in the regulation of the sieve tube system (Ma et al, 2010).…”