A multifaceted study of stigma/style cysteine-rich adhesin (SCA)-like Arabidopsis lipid transfer proteins (LTPs) suggests diversified roles for these LTPs in plant growth and reproduction

Abstract

Lily stigma/style cysteine-rich adhesin (SCA), a plant lipid transfer protein (LTP) which is secreted into the extracellular matrix, functions in pollen tube guidance in fertilization. A gain-of-function mutant (ltp5-1) for Arabidopsis LTP5, an SCA-like molecule, was recently shown to display defects in sexual reproduction. In the current study, it is reported that ltp5-1 plants have dwarfed primary shoots, delayed hypocotyl elongation, various abnormal tissue fusions, and display multibranching. These mutant phenotypes in vegetative growth are recessive. No abnormality was found in ltp5-1/+ plants. In a phylogenetic analysis of plant LTPs, SCA-like Arabidopsis LTPs were classified with conventional plant LTPs. Homology modelling-based electrostatic similarity index (ESI) clustering was used to show diversity in spatial distributions of electrostatic potentials of SCA-like LTPs, suggestive of their various roles in interaction in the extracellular matrix space. β-Glucuronidase (GUS) analysis showed that SCA-like Arabidopsis LTP genes are diversely present in various tissues. LTP4 was found specifically in the guard cells and LTP6 in trichomes as well as in other tissues. LTP1 levels were specifically abundant in the stigma, and both LTP3 and LTP6 in the ovules. LTP2 and LTP4 gene levels were up-regulated in whole seedlings with 20% polyethylene glycol (PEG) and 300 mM NaCl treatments, respectively. LTP5 was up-regulated in the hypocotyl with 3 d dark growth conditions. LTP6 was specifically expressed in the tip of the cotyledon under drought stress conditions. The results suggest that SCA-like Arabidopsis LTPs are multifunctional, with diversified roles in plant growth and reproduction.

Computational study of ligand binding in lipid transfer proteins: Structures, interfaces, and free energies of protein‐lipid complexes

“…Recently reported evidence on the possible multifunctionality of nsLTPs in plant growth processes [6][7][8] and open questions on the antigenic interactions of plant nsLTPs in alimentary allergies (particularly peach nsLTP), [58][59][60][61] pose the need to deepen our understanding on their lipid binding properties. In addition, we aimed to gain insight into general protein-ligand interactions by providing quantitative information on the lipid binding abilities of these small proteins.…”

“…Although there is a large literature on these proteins and their possible functions have been largely debated over the years (for a review see Salcedo et al [6] ), new roles for nsLTPs are still being proposed. Recent reports on the functions of nsLTPs in cuticular wax deposition [7] or the suggestion that they should be multifunctional in plant growth and organ development [8] have posed new questions on their roles in plants.…”

“…Recent reports on new possible roles of LTPs [7,8] have highlighted the presence of these small proteins in extracellular matrix (ECM) regions where disparate molecules with negatively charged moieties are abundant. [8] NsLTPs have net positive charge and generate electrostatic potentials predominantly positive (see below), which must be related with their distribution in the ECM. The possible multifunctional roles of nsLTPs on plant growth processes should be related with their ability to bind a broad variety of lipids.…”

Functional network analysis of genes differentially expressed during xylogenesis insoc1fulwoody Arabidopsis plants

“…In addition, genes encoding two key enzymes involved in providing UDP-glucose for cellulose and xylan biosynthesis, SUS3 and SUS4, were preferentially expressed during cambium formation (Baroja-Fernandez et al, 2012). LTP1 and LTP2, which are attributed to cell wall loosening, are upregulated (Chae et al, 2010). Finally, three hydroxyproline-rich glycoproteins (HRGP), PELPK1 (Rashid and Deyholos, 2011), AT5G09480 and AT4G38080, were preferentially expressed in the cambium samples compared with herbaceous developmental stages, especially in the mutant (>5 log 2 -fold in soc1ful; Table 1).…”

CYCLIN H;1 Regulates Drought Stress Responses and Blue Light-Induced Stomatal Opening by Inhibiting Reactive Oxygen Species Accumulation in Arabidopsis

“…Under water-sufficient conditions, only 49 genes showed more than a 2-fold change in expression, of which 35 were up-regulated and 14 were down- regulated in the cych;1 RNAi#7 mutant ( Table I). The microarray results indicated increased transcript levels of ARABIDOPSIS RIBULOSE-BISPHOSPHATE CAR-BOXYLASE/OXYGENASE X1 (ATRBCX1) (Kolesinski et al, 2011), ECERIFERUM1 (CER1) (Bourdenx et al, 2011), JASMONATE-ZIM-DOMAIN PROTEIN5 (JAZ5; Pauwels and Goossens, 2011), LIPID TRANSFER PROTEIN2 (LTP2; Chae et al, 2010), and At1g06620 in the cych;1 RNAi#7 mutant, all of which can be induced by water deprivation. Interestingly, the 35 upregulated genes included at least 12 genes involved in redox homeostasis (i.e.…”