The structure of “defective in induced resistance” protein of Arabidopsis thaliana, DIR1, reveals a new type of lipid transfer protein

Abstract

Screening of transfer DNA (tDNA) tagged lines of Arabidopsis thaliana for mutants defective in systemic acquired resistance led to the characterization of dir1-1 (defective in induced resistance [systemic acquired resistance, SAR]) mutant. It has been suggested that the protein encoded by the dir1 gene, i.e., DIR1, is involved in the long distance signaling associated with SAR. DIR1 displays the cysteine signature of lipid transfer proteins, suggesting that the systemic signal could be lipid molecules. However, previous studies have shown that this signature is not sufficient to define a lipid transfer protein, i.e., a protein capable of binding lipids. In this context, the lipid binding properties and the structure of a DIR1-lipid complex were both determined by fluorescence and X-ray diffraction. DIR1 is able to bind with high affinity two monoacylated phospholipids (dissociation constant in the nanomolar range), mainly lysophosphatidyl cholines, side-by-side in a large internal tunnel. Although DIR1 shares some structural and lipid binding properties with plant LTP2, it displays some specific features that define DIR1 as a new type of plant lipid transfer protein. The signaling function associated with DIR1 may be related to a specific lipid transport that needs to be characterized and to an additional mechanism of recognition by a putative receptor, as the structure displays on the surface the characteristic PxxP structural motif reminiscent of SH3 domain signaling pathways.

The effects of putrescine are partly overlapping with osmotic stress processes in wheat

“…In the present study a bifunctional inhibitor/lipid-transfer protein/seed storage 2S albumin superfamily protein (Dir1) [56] and PLAT/LH2 domain-containing lipoxygenase have been upregulated not only under osmotic stress, but after PUT pre-treatment, while the highest induction was found after PUT pre-treated + PEG treatment. The PLAT/LH2 domain-containing lipoxygenase also has a role in plant signalling, as it was reported to be induced by ABA, SA, jasmonate or wounding [57].…”

GLK Transcription Factors Coordinate Expression of the Photosynthetic Apparatus in Arabidopsis

“…WoLF PSORT weakly predicts that MRU1 is targeted to the mitochondrion, followed by equal probability of being targeted to the chloroplast, cytosol, or peroxisome. Similarly, the lipid transfer protein (LTP) encoded by At5g48490 putatively functions in lipid binding and transport (Lascombe et al, 2008), which may reflect a requirement for thylakoid lipids. The increased expression of COR15a and a thylakoid lumen-resident rhodanese-like domain-containing protein (At2g42220) following GLK induction is particularly intriguing.…”

Plant lipid transfer proteins: Evolution, expression and function

“…Several years later the smaller (usually 7 kDa) Type 2 was found in barley and wheat (Castagnaro and Garcia-Olmedo, 1994;Kalla et al, 1994). The two original types have persisted through time, but more recently several additional types have been found (Boutrot et al, 2008;Lascombe et al, 2008). It is not yet clear whether the different types differ in function or lipid preferences.…”

“…2). The eight cysteines are involved in four intramolecular disulphide bridges that stabilize the tertiary structure of the protein (Shin et al, 1995;Lascombe et al, 2008). Thus, the nsLTPs are very stable to heat and different denaturing agents (Lindorff-Larsen and Winther, 2001).…”

“…The crystal structure has been determined for several nsLTPs, among them one from peach, one from rice, one from Arabidopsis and one from maize (Gomar et al, 1996;Poznanski et al, 1999;Lascombe et al, 2008). The structural studies have determined that the folding of nsLTP proteins occurs in two different ways, namely the Type 1 and the Type 2 fold.…”