Genome-Wide Analysis of the Fasciclin-Like Arabinogalactan Protein Gene Family Reveals Differential Expression Patterns, Localization, and Salt Stress Response in Populus

Abstract

Fasciclin-like arabinogalactan proteins (FLAs) are a subclass of arabinogalactan proteins (AGPs) involved in plant growth, development and response to abiotic stress. Although many studies have been performed to identify molecular functions of individual family members, little information is available on genome-wide identification and characterization of FLAs in the genus Populus. Based on genome-wide analysis, we have identified 35 Populus FLAs which were distributed on 16 chromosomes and phylogenetically clustered into four major groups. Gene structure and motif composition were relatively conserved in each group. All the members contained N-terminal signal peptide, 23 of which included predicted glycosylphosphatidylinositol (GPI) modification sites and were anchored to plasma membranes. Subcellular localization analysis showed that PtrFLA2/20/26 were localized in cell membrane and cytoplasm of protoplasts from Populus stem-differentiating xylem. The Ka/Ks ratios showed that purifying selection has played a leading role in the long-term evolutionary period which greatly maintained the function of this family. The expression profiles showed that 32 PtrFLAs were differentially expressed in four tissues at four seasons based on publicly available microarray data. 18 FLAs were further verified with qRT-PCR in different tissues, which indicated that PtrFLA1/2/3/7/11/12/20/21/22/24/26/30 were significantly expressed in male and female flowers, suggesting close correlations with the reproductive development. In addition, PtrFLA1/9/10/11/17/21/23/24/26/28 were highly expressed in the stems and differentiating xylem, which may be involved in stem development. To determine salt response of FLAs, qRT-PCR was performed to analyze the expression of 18 genes under salinity stress across two time points. Results demonstrated that all the 18 FLAs were expressed in root tissues; especially, PtrFLA2/12/20/21/24/30 were significantly induced at different time points. In summary, this study may lay the foundation for further investigating the biological functions of FLA genes in Populus trichocarpa.

Plant Cell Walls Tackling Climate Change: Biotechnological Strategies to Improve Crop Adaptations and Photosynthesis in Response to Global Warming

“…In Populus, 18 FLAs were expressed in root tissues under salt stress. Importantly, six of them, PtrFLA2, PtrFLA12, PtrFLA20, PtrFLA21, PtrFLA24, and PtrFLA30, were significantly induced at different time points which could indicate a FLA role in salt stress response [132]. FERONIA (FER), a plasma-membrane-localized receptor kinase, senses defects in pectin structure and wall elasticity caused by high salinity in order to activate signaling pathways [133].…”

Field Guide to Plant Model Systems

“…Poplar is a valuable source of timber because of its rapid growth, maturing in ~5 years. Genome information from poplar has been used to study wood formation, salt stress, and other relevant characteristics (Dharmawardhana et al, 2010; Wullschleger et al, 2013; Zang et al, 2015). The genome sequences of the fast-growing hardwood trees, Eucalyptus grandis (640 Mb) and E. globulus (530 Mb), offer the opportunity for comparative angiosperm tree genomics as well as investigation of specialized metabolites, such as terpenes and oils (Myburg et al, 2014).…”

Fasciclin-like arabinogalactan gene family in Nicotiana benthamiana: genome-wide identification, classification and expression in response to pathogens

“…The predicted isoelectric points range from 4.29 to 9.77, and the molecular weights (MWs) are in the range 19.68-52.32 kDa. The protein properties of the NbFLAs are similar to those of other plant species [8,11].…”

“…So far, the FLA family members have been identified in several plant species. 21 FLAs have been identified in Arabidopsis thaliana [8], 27 in rice (Oryza sativa) [9,10], 34 in wheat (Triticum aestivum) [10], 35 in poplar (Populus trichocarpa) [11], 19 in cotton (Gossypium hirsutum) [12], 33 in Chinese cabbage (Brassica rapa) [13], 18 in Eucalyptus grandis [14] and 23 in textile hemp (Cannabis sativa) [15]. FLAs are cell wall structural glycoproteins that mediate cellulose deposition and cell wall development.…”