Molecular Analyses of the Arabidopsis TUBBY-Like Protein Gene Family

Abstract

In mammals, TUBBY-like proteins play an important role in maintenance and function of neuronal cells during postdifferentiation and development. We have identified a TUBBY-like protein gene family with 11 members in Arabidopsis, named AtTLP1-11. Although seven of the AtTLP genes are located on chromosome I, no local tandem repeats or gene clusters are identified. Except for AtTLP4, reverse transcription-PCR analysis indicates that all these genes are expressed in various organs in 6-week-old Arabidopsis. AtTLP1, 2, 3, 6, 7, 9, 10, and 11 are expressed ubiquitously in all the organs tested, but the expression of AtTLP5 and 8 shows dramatic organ specificity. These 11 family members share 30% to 80% amino acid similarities across their conserved C-terminal tubby domains. Unlike the highly diverse N-terminal region of animal TUBBY-like proteins, all AtTLP members except AtTLP8 contain a conserved F-box domain (51–57 residues). The interaction between AtTLP9 and ASK1 (Arabidopsis Skp1-like 1) is confirmed via yeast (Saccharomyces cerevisiae) two-hybrid assays. Abscisic acid (ABA)-insensitive phenotypes are observed for two independent AtTLP9 mutant lines, whereas transgenic plants overexpressing AtTLP9 are hypersensitive to ABA. These results suggest that AtTLP9 may participate in the ABA signaling pathway.

Comparative Proteomics Analysis of Differentially Expressed Proteins in Chickpea Extracellular Matrix during Dehydration Stress

“…It is also an important component for maintaining stable GTP levels through nucleotide homeostasis in various GTP-mediated signal transduction pathways (31). The tubbylike protein (CaE-61) was found to be up-regulated at 72 h. It belongs to the F-box family proteins that encode transcription factors and is known in animals to shuttle between the plasma membrane and the nucleus on environmental cue (32). Unusual proteins like translation initiation factor were also observed that may play a more diverse role in ECM than in its classical com-TABLE II-continued a Spot number as given on the 2-D gel images.…”

The E3 Ubiquitin Ligase Gene Family in Plants: Regulation by Degradation

“…Many studies have supplied evidences that the most of the genes coding for E3 ubiquitin ligases are indeed active in a number of plant tissues: nearly all RING, U-box, ASK and BTB proteins are expressed [26,44,48,49,60], while only for less than half F-box genes there is an evidence of expression [50,61]. Some E3 ubiquitin ligases or E3 components are ubiquitously expressed in all analysed tissues, while others show more restricted expression patterns which could be related to a particular function in plant development.…”

E3 ubiquitin ligases and abscisic acid signaling

“…F-box protein AtTLP9, a member of the Arabidopsis TUBBY-LIKE family, interacts with Arabidopsis Skp1-like 1 (ASK1), a cullin binding protein, suggesting that AtTLP9 acts as a substrate recognition subunit in a SCF E3 ligase complex. 43 AtTLP9 mutant lines display an ABA insensitive phenotype during seed germination assays, whereas transgenic plants overexpressing AtTLP9 are hypersensitive to ABA. These results suggest that AtTLP9 is involved in modulating ABA-mediated responses, probably by targeting a negative regulator of ABA signaling for degradation.…”

“…These results suggest that AtTLP9 is involved in modulating ABA-mediated responses, probably by targeting a negative regulator of ABA signaling for degradation. 43 The involvement of another SCF E3 complex in ABA signaling was uncovered through characterization of Drought Tolerance Repressor (DOR), a putative F-box protein, which interacts with ASK14 and CUL1. 44 A null mutation in DOR results in a hypersensitive response to ABA during stomatal closing and a substantial increase in drought tolerance.…”