The BURP domain protein AtUSPL1 of Arabidopsis thaliana is destined to the protein storage vacuoles and overexpression of the cognate gene distorts seed development

Abstract

BURP domain proteins comprise a broadly distributed, plant-specific family of functionally poorly understood proteins. VfUSP (Vicia faba Unknown Seed Protein) is the founding member of this family. The BURP proteins are characterized by a highly conserved C-terminal protein domain with a characteristic cysteine-histidine pattern. The Arabidopsis genome contains five BURP-domain encoding genes. Three of them are similar to the non-catalytic beta-subunit of the polygalacturonase of tomato and form a distinct subgroup. The remaining two genes are AtRD22 and AtUSPL1. The deduced product of AtUSPL1 is similar in size and sequence to VfUSP and that of the Brassica napus BNM2 gene which is expressed during microspore-derived embryogenesis. The protein products of BURP genes have not been found, especially that of VfUSP despite a great deal of interest arising from copious transcription of the gene in seeds. Here, we demonstrate that VfUSP and AtUSPL1 occur in cellular compartments essential for seed protein synthesis and storage, like the Golgi cisternae, dense vesicles, prevaculoar vesicles and the protein storage vacuoles in the parenchyma cells of cotyledons. Ectopic expression of AtUSPL1 leads to a shrunken seed phenotype; these seeds show structural alterations in their protein storage vacuoles and lipid vesicles. Furthermore, there is a reduction in the storage protein content and a perturbation in the seed fatty acid composition. However, loss of AtUSP1 gene function due to T-DNA insertions does not lead to a phenotypic change under laboratory conditions even though the seeds have less storage proteins. Thus, USP is pertinent to seed development but its role is likely shared by other proteins that function well enough under the laboratory growth conditions.

Low red/far-red ratios delay spike and stem growth in wheat

“…3) and concomitantly reduced the expression of genes expressed preferentially in the spike (Fig. 6), including three putative zinc-finger proteins (Kobayashi et al , 1998; Nakagawa et al , 2004), a BURP-domain protein gene (Batchelor et al , 2002; Van Son et al , 2009), ABSCISIC ACID INSENSITIVE 5 ABI5 (Gutierrez et al , 2007), a dehydrin (Black et al , 1999), and DOF1 (Mena et al , 1998), previously linked to floral organ or seed development. A low R/FR ratio reduced the number of fertile florets at anthesis (Fig.…”

Genome-scale identification of Soybean BURP domain-containing genes and their expression under stress treatments

“…), transports sporopollenin from tapetum to developing microspores via Ubisch bodies [13]. AtUSPL1 occurs in cellular compartments such as Golgi cisternae, dense vesicles, prevaculoar vesicles and the protein storage vacuoles in the parenchyma cell of cotyledons, and thus may play a role in seed development [14]. So it seems that many BURP family members play a role in maintaining the normal metabolism or development in plants.…”

Expression of a Vacuole-Localized BURP-Domain Protein from Soybean (SALI3-2) Enhances Tolerance to Cadmium and Copper Stresses

“…A number of BURP genes have been identified. In addition to those genes that were sporadically isolated in special tissues, developmental stages or conditions [4], [5], [6], [7], [8], 5 members in Arabidopsis thaliana [9], 17 in Oryza sativa L. [10], 23 in Glycine max [11], 15 in Zea mays , 11 in Sorghum vulgare [12] and 18 in Populus trichocarpa [13] were identified genome-widely. The expression of these genes exhibits different temporal and spatial profiles [7], [10], and some of them can be regulated by various stress treatments [10], [11], [14], suggesting that BURP genes might play diverse roles in plant development and stress responses.…”

“…Some BURP proteins function in particular intracellular compartments. For example, AtUSP in Arabidopsis thaliana [9] and BNM2 in Brassica napus [15], are most likely localized in cellular compartments such as the Golgi cisternae, dense vesicles, prevaculoar vesicles and protein storage vacuoles. These proteins are related to seed protein synthesis and storage and seed development.…”