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Structural and functional characterization of peanut expansin proteins identifies AhEXPA3 as a stress-responsive regulator of seed germination.

Expansins are cell wall-associated proteins that play important roles in plant growth, development, and environmental responses, yet their structural features and functional significance in peanut remain insufficiently understood. Here, we performed a genome-wide identification and characterization of 70 expansin proteins in cultivated peanut. Phylogenetic analysis classified these genes into four subfamilies (EXPA, EXPB, EXLA, and EXLB), with conserved motif patterns and subgroup-specific exon-intron structures. Collinearity and evolutionary analyses revealed that segmental duplication mainly drove peanut expansin family expansion, with most duplicated gene pairs subsequently undergoing purifying selection. Promoter analysis identified abundant cis-regulatory elements associated with light responses, hormone signaling, and stress responses. Expression profiling indicated that many AhEXP genes were differentially expressed during seed germination and in response to abscisic acid (ABA), salt, and osmotic stresses. Among them, AhEXPA3 was identified as a stress-responsive expansin protein with marked transcriptional induction under abiotic stress conditions. Subcellular localization analysis suggested that AhEXPA3 exhibits an endoplasmic reticulum-associated localization pattern. Functional assays further demonstrated that heterologous expression of AhEXPA3 inhibited seed germination and early seedling establishment under stress conditions in both Arabidopsis thaliana and rice. These findings support a negative regulatory role of AhEXPA3 in stress-responsive seed germination and broaden current understanding of expansin protein function in legumes.

Germination

Genome-wide identification of the expansin gene family in Rosa rugosa and overexpression of RrEXPA1 contributes to drought and salt stress tolerance in Arabidopsis.

The expansin (EX) gene family plays a crucial role in the growth and development of various plants, as well as responses to biotic and abiotic stresses. However, genome-wide analysis of the EX gene family and their functions in drought and salt stress tolerance has not been examined in Rosa rugosa. In this study, a total of 30 RrEX genes were identified and located on seven different chromosomes. Phylogenetic analysis classified these genes into four subfamilies: EXPA (24 members), EXPB (3 members), EXLA (1 member), and EXLB (2 members). The average amino acid length was 269.17 aa, with isoelectric points ranging from 4.79 to 9.97. Most members exhibited high aliphatic indices and protein stability, suggesting their adaptability to diverse environments. The synteny analysis provided insights into the evolution of the EX gene family in rose. Toxicity and autoactivation assays confirmed that BD-RrEXPA1 was non-toxic to yeast cells and lacked autoactivation activity, indicating its suitability for yeast two-hybrid screening. The transgenic Arabidopsis lines overexpressing RrEXPA1 improved seed germination and root length under abiotic stress. In addition, the overexpression lines showed reduced malondialdehyde (MDA) levels and increased chlorophyll content and superoxide dismutase (SOD) activity. These results suggest that RrEXPA1 may enhance stress tolerance by promoting root elongation and modulating physiological responses. This study provides important insights into the role of RrEXs in salt and drought stress and lays the foundation for further studies on the regulatory mechanisms of abiotic stress.

Drought stress

Continuous flow synthesis of peptides using a polyacrylamide gel resin (Expansin).

The continuous flow syntheses of endothelin 1, proendothelin 2, ATP binding site of the CDC2 kinase 3, and fragment 18-30 of an actin 4, have been performed by using a polyacrylamide gel resin Expansin (about 0.6 mmol NH2/g) with the glycolamidic ester handle as labile anchorage. In addition, we report here a method of air oxidation which reduces the formation of side-products related to the formation of intermolecular disulfide bridges.

Acrylic Resins

Seed shattering habit in millets and the secrets of the abscission layer - a comprehensive review.

Though seed shattering continues to be a significant barrier affecting yield stability and harvesting efficiency in millets and other grasses, millets are increasingly acknowledged as climate-resilient, nutrient-rich 2007cereal crops with the potential to strengthen global nutritional and food security under the combined pressures of climate change, population growth, and limited natural resources. Since strong artificial selection favoured non-shattering phenotypes during domestication, seed shattering, an adaptive trait in wild species that promotes seed dispersal through the formation and activation of specialised abscission layers, became a distinguishing feature of cultivated cereals. With a focus on the morphological, physiological, hormonal, and genetic modulation of the abscission zone, this article summarizes the state of the art regarding seed shattering in millets. Abscission layer morphology, location, and lignification vary greatly among grasses, from well-defined lignified zones in rice and sorghum to non-lignified and anatomically subtle zones in Setaria and Panicum species. Cell wall-modifying enzymes like polygalacturonases, cellulases, expansins, and pectin methylesterases that mediate middle lamella degradation are modulated by coordinated hormonal signalling involving auxin, ethylene, and abscisic acid, which controls the timing and progression of cell separation at the physiological level. Domestication-related genes, including SH1, qSH1, SH4, and LES1, demonstrate convergent evolutionary mechanisms controlling abscission layer development in a variety of grass lineages at the molecular level. Understanding these regulatory networks has been greatly enhanced by recent developments in transcriptomics, functional genomics, and genome sequencing in both model species and underused millets. The role of millets as climate-smart cereals for sustainable future agriculture is reinforced by the integration of anatomical, physiological, and genetic insights, which offer a solid basis for targeted breeding and genome-editing strategies intended to improve seed retention, enhance yield stability, and increase harvest efficiency.

Abscission Layer

Role of functional genes for seed vigor related traits through genome-wide association mapping in finger millet (Eleusine coracana L. Gaertn.).

Finger millet (Eleusine coracana (L.) Gaertn.) is a calcium-rich, nutritious and resilient crop that thrives even in harsh environmental conditions. In such ecologies, seed longevity and seedling vigor are crucial for sustainable crop production amid climate change. The current study explores the genetics of accelerated aging on seed longevity traits across 221 diverse accessions of finger millet through genome-wide association approach (GWAS). A significant variation was identified in germination percentage, germination rate indices, mean germination time, seedling vigor indices and dry weight upon aging treatment. GWAS model from 11,832 high-quality SNPs identified through Genotyping-by-Sequencing (GBS) approach produced 491 marker-trait associations (MTAs) for 27 traits, of which 54 were FDR-corrected. A pleiotropic SNP, FM_SNP_9478 identified on chromosome 7B was associated with the traits viz., germination after aging, germination index after aging and their relative measures. Functional annotation revealed DET1 and expansin-A2 influenced seed coat integrity, critical for germination and aging resilience. Probable protein phosphatase 2C3 and piezo-type ion channels contributed to mechanical sensing and stress adaptation in seeds. Beta-amylase and acetyl-CoA carboxylase 2 were identified for seed metabolism and stress response. These insights lay the framework for targeted breeding efforts to improve seed quality and resilience under diverse production conditions.

Eleusine

Disulfide bond as peptide-resin linkage in Boc-Bzl SPPS, for potential biochemical applications.

Use of disulfide bonds for labile linkage in solid-phase peptide synthesis was investigated using polyacrylic polymers (Expansin). Three bifunctional disulfide handles were synthesized for the introduction of disulfide linkage to the synthesis support. This work showed that only N-Boc aminoethyl 2-propionic acid and N-Boc aminoethyl 2-isobutyric acid were fully compatible with Boc/Bzl peptide synthesis and trifluoromethane sulfonic acid side-chain protection. Qualitative and quantitative synthesis results were comparable to those obtained by conventional peptide synthesis using polyacrylic resins. The resulting peptidyl-resins, which swelled in water or aqueous buffers, may be suitable for various biochemical applications, including use as peptide-resin conjugates for antibody production. Thiolysis by aqueous dithiothreitol released mercapto amide peptides suitable for various uses in solution (e.g., direct coupling with activated protein carrier, specific labeling in the mercapto amide group). Partial thiolysis of the disulfide linkage allowed easy post-synthetic adjustment of the peptide loading of peptidyl-resins.

Amino Acid Sequence