Abstract
The Translationally Controlled Tumor Protein (TCTP) is a central regulator of cell proliferation and differentiation in animals, and probably also in plants. Arabidopsis harbors two TCTP genes, AtTCTP1 (At3g16640), which is an important mitotic regulator, and AtTCTP2 (At3g05540), which is considered a pseudogene. Nevertheless, we have obtained evidence suggesting that this gene is functional. Indeed, a T-DNA insertion mutant, SALK_045146, displays a lethal phenotype during early rosette stage. Also, both the AtTCTP2 promoter and structural gene are functional, and heterozygous plants show delayed development. AtTCTP1 cannot compensate for the loss of AtTCTP2, since the accumulation levels of the AtTCTP1 transcript are even higher in heterozygous plants than in wild-type plants. Leaf explants transformed with Agrobacterium rhizogenes harboring AtTCTP2, but not AtTCTP1, led to whole plant regeneration with a high frequency. Insertion of a sequence present in AtTCTP1 but absent in AtTCTP2 demonstrates that it suppresses the capacity for plant regeneration; also, this phenomenon is enhanced by the presence of TCTP (AtTCTP1 or 2) in the nuclei of root cells. This confirms that AtTCTP2 is not a pseudogene and suggests the involvement of certain TCTP isoforms in vegetative reproduction in some plant species.
Highlights
The Translationally Controlled Tumor Protein (TCTP) is a conserved family found in most eukaryotes, which has a central role in growth and developmental regulation
The severity of the phenotype correlated with decreased levels of AtTCTP2 mRNA in different heterozygous lines, while those for AtTCTP1 mRNA did not show such correlation, in all cases were higher than in WT plants (Figure 2)
We have shown that the Cucurbita maxima phloem TCTP (CmTCTP) induces an increase in biomass; it induces whole plant regeneration in tobacco when harbored by Agrobacterium rhizogenes K599 (Hinojosa-Moya et al, 2013)
Summary
The Translationally Controlled Tumor Protein (TCTP) is a conserved family found in most eukaryotes, which has a central role in growth and developmental regulation. The precise role of TCTP is not completely clear, because mutants are pleiotropic; its Arabidopsis AtTCTP2 induces whole-plant regeneration involvement in cell proliferation and development is likely (Amson et al, 2013). There is less information regarding the function of TCTP in plants, but most evidence points to a central role in regulating proliferation and development. Arabidopsis AtTCTP1 (At3g16640) mutants show a lethal phenotype in early stages of embryo development, and silenced lines show defects in cell size, root structure, and pollen (Berkowitz et al, 2008; Brioudes et al, 2010). AtTCTP1 overexpression protects against apoptotic cell death triggered by different effectors in plants (Hoepflinger et al, 2013)
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