Localization of tobacco germin-like protein 1 in leaf intercellular space

Divergent structures and functions of the Cupin proteins in plants

Cupin superfamily proteins have extensive functions. Their members are not only involved in the development of plants but also responded to various stresses. Whereas, the research on the Cupin members has not attracted enough attention. In this article, we summarized the research progress on these family genes in recent years and explored their evolution, structural characteristics, and biological functions. The significance of members of the Cupin family in the development of plant cell walls, roots, leaves, flowers, fruits, and seeds and their role in stress response are highlighted. Simultaneously, the prospective application of Cupin protein in crop enhancement was introduced. Some members can enhance plant growth, development, and resistance to adversity, thereby increasing crop yield. It will be as a foundation for future effective crop research and breeding.

PdeHCA2 affects biomass in Populus by regulating plant architecture, the transition from primary to secondary growth, and photosynthesis

PdeHCA2 regulates the transition from primary to secondary growth, plant architecture, and affects photosynthesis by targeting PdeBRC1 and controlling the anatomy of the mesophyll, and intercellular space, respectively. Branching, secondary growth, and photosynthesis are vital developmental processes of woody plants that determine plant architecture and timber yield. However, the mechanisms underlying these processes are unknown. Here, we report that the Populus transcription factor High Cambium Activity 2 (PdeHCA2) plays a role in the transition from primary to secondary growth, vascular development, and branching. In Populus, PdeHCA2 is expressed in undifferentiated provascular cells during primary growth, in phloem cells during secondary growth, and in leaf veins, which is different from the expression pattern of its homolog in Arabidopsis. Overexpression of PdeHCA2 has pleiotropic effects on shoot and leaf development; overexpression lines showed delayed growth of shoots and leaves, reduced photosynthesis, and abnormal shoot branching. In addition, auxin-, cytokinin-, and photosynthesis-related genes were differentially regulated in these lines. Electrophoretic mobility shift assays and transcriptome analysis indicated that PdeHCA2 directly up-regulates the expression of BRANCHED1 and the MADS-box gene PdeAGL9, which regulate plant architecture, by binding to cis-elements in the promoters of these genes. Taken together, our findings suggest that HCA2 regulates several processes in woody plants including vascular development, photosynthesis, and branching by affecting the proliferation and differentiation of parenchyma cells.

Identification and characterization of two germin-like proteins with oxalate oxidase activity from Calotropis procera latex

Germin-like proteins (GLPs) have been identified in several plant tissues. However, only one work describes GLP in latex fluids. Therefore, the goal of this study was to investigate GLPs in latex and get new insights concerning the structural and functional aspects of these proteins. Two complete sequences with high identity (>50%) with other GLPs, termed CpGLP1 and CpGLP2, were obtained and consecutively presented 216 and 206 amino acid residues, corresponding to molecular masses of 22.7 and 21.7kDa, pI 6.8 and 6.5. The three-dimensional models revealed overall folding similar to those reported for other plant GLPs. Both deduced sequences were grouped into the GER 2 subfamily. Molecular docking studies indicated a putative binding site consisting of three highly conserved histidines and a glutamate residue, which interacted with oxalate. This interaction was later supported by enzymatic assays. Superoxide dismutase (common activity in GLPs) was not detected for CpGLP1 and CpGLP2 by zymogram. The two proteins were detected in the latex, but not in non-germinated or germinated seeds and calli. These results give additional support that germin-like proteins are broadly distributed in plants and they are tissue-specific. This particularity deserves further studies to better understand their functions in latex.

Monoclonal antibody-based analysis of cell wall remodeling during xylogenesis

Xylogenesis, a process by which woody tissues are formed, entails qualitative and quantitative changes in the cell wall. However, the molecular events that underlie these changes are not completely understood. Previously, we have isolated two monoclonal antibodies, referred to as XD3 and XD27, by subtractive screening of a phage-display library of antibodies raised against a wall fraction of Zinnia elegans xylogenic culture cells. Here we report the biochemical and immunohistochemical characterization of those antibodies. The antibody XD3 recognized (1→4)-β-D-galactan in pectin fraction. During xylogenesis, the XD3 epitope was localized to the primary wall of tracheary-element precursor cells, which undergo substantial cell elongation, and was absent from mature tracheary elements. XD27 recognized an arabinogalactan protein that was bound strongly to a germin-like protein. The XD27 epitope was localized to pre-lignified secondary walls of tracheary elements. Thus these cell-wall-directed monoclonal antibodies revealed two molecular events during xylogenesis. The biological significance of these events is discussed in relation to current views of the plant cell wall.

Transcriptome-Wide Identification of miRNA Targets under Nitrogen Deficiency in Populus tomentosa Using Degradome Sequencing

miRNAs are endogenous non-coding small RNAs with important regulatory roles in stress responses. Nitrogen (N) is an indispensable macronutrient required for plant growth and development. Previous studies have identified a variety of known and novel miRNAs responsive to low N stress in plants, including Populus. However, miRNAs involved in the cleavage of target genes and the corresponding regulatory networks in response to N stress in Populus remain largely unknown. Consequently, degradome sequencing was employed for global detection and validation of N-responsive miRNAs and their targets. A total of 60 unique miRNAs (39 conserved, 13 non-conserved, and eight novel) were experimentally identified to target 64 mRNA transcripts and 21 precursors. Among them, we further verified the cleavage of 11 N-responsive miRNAs identified previously and provided empirical evidence for the cleavage mode of these miRNAs on their target mRNAs. Furthermore, five miRNA stars (miRNA*s) were shown to have cleavage function. The specificity and diversity of cleavage sites on the targets and miRNA precursors in P. tomentosa were further detected. Identification and annotation of miRNA-mediated cleavage of target genes in Populus can increase our understanding of miRNA-mediated molecular mechanisms of woody plants adapted to low N environments.