Systematic analysis of lysine 2-hydroxyisobutyrylation posttranslational modification in wheat leaves

Identification and Functional Analysis of Lysine 2-Hydroxyisobutyrylation in Cyanobacteria

Cyanobacteria are the oldest prokaryotic photoautotrophic microorganisms and have evolved complicated post-translational modification (PTM) machinery to respond to environmental stress. Lysine 2-hydroxyisobutyrylation (Khib) is a newly identified PTM that is reported to play important roles in diverse biological processes, however, its distribution and function in cyanobacteria have not been reported. Here, we performed the first systematic studies of Khib in a model cyanobacterium Synechococcus sp. strain PCC 7002 (Syn7002) using peptide prefractionation, pan-Khib antibody enrichment, and high-accuracy mass spectrometry (MS) analysis. A total of 1875 high-confidence Khib sites on 618 proteins were identified, and a large proportion of Khib sites are present on proteins in the cellular metabolism, protein synthesis, and photosynthesis pathways. Using site-directed mutagenesis and functional studies, we showed that Khib of glutaredoxin (Grx) affects the efficiency of the PS II reaction center and H2O2 resistance in Syn7002. Together, this study provides novel insights into the functions of Khib in cyanobacteria and suggests that reversible Khib may influence the stress response and photosynthesis in both cyanobacteria and plants.

Functions of lysine 2-hydroxyisobutyrylation and future perspectives on plants

Lysine 2-hydroxyisobutyrylation (Khib) is a novel protein post-translational modifications (PTMs) observed in both eukaryotes and prokaryotes. Recent studies suggested that this novel PTM has the potential to regulate different proteins in various pathways. Khib is regulated by lysine acyltransferases and deacylases. This novel PTM reveals interesting connections between modifications and protein physiological functions, including gene transcription, glycolysis and cell growth, enzymic activity, sperm motility, and aging. Here, we review the discovery and the current understanding of this PTM. Then, we outline the networks of complexity of interactions among PTMs in plants, and raise possible directions of this novel PTM for future investigations in plants.

More than the main structural genes: Regulation of resistant starch formation in rice endosperm and its potential application

In the past decade, research on resistant starch has evoked interest due to the prevention and inhibition of chronic human diseases, such as diabetes, cancer, and obesity. Increasing the amylose content (AC) and resistant starch (RS) has been pivotal in improving the nutritional benefit of rice. However, the exact mechanism of RS formation is complex due to interconnected genetic factors regulating amylose-amylopectin variation. In this review, we discussed the regulatory factors influencing the RS formation centered on the transcription, post-transcriptional, and post-translational processes. Furthermore, we described the developments in RS and AC levels in rice compared with other high RS cereals. Briefly, we enumerated potential applications of high RS mutants in health, medical, and other industries. We contest that the information captured herein can be deployed for marker-assisted breeding and precision breeding techniques through genome editing to improve rice varieties with enhanced RS content.

Proteomic analysis of protein lysine 2-hydroxyisobutyrylation (Khib) in soybean leaves

BACKGROUND

Protein lysine 2-hydroxyisobutyrylation (K_hib) is a novel post-translational modification (PTM) discovered in cells or tissues of animals, microorganisms and plants in recent years. Proteome-wide identification of K_hib-modified proteins has been performed in several plant species, suggesting that K_hib-modified proteins are involved in a variety of biological processes and metabolic pathways. However, the protein K_hib modification in soybean, a globally important legume crop that provides the rich source of plant protein and oil, remains unclear.

RESULTS

In this study, the K_hib-modified proteins in soybean leaves were identified for the first time using affinity enrichment and high-resolution mass spectrometry-based proteomic techniques, and a systematic bioinformatics analysis of these K_hib-modified proteins was performed. Our results showed that a total of 4251 K_hib sites in 1532 proteins were identified as overlapping in three replicates (the raw mass spectrometry data are available via ProteomeXchange with the identifier of PXD03650). These K_hib-modified proteins are involved in a wide range of cellular processes, particularly enriched in biosynthesis, central carbon metabolism and photosynthesis, and are widely distributed in subcellular locations, mainly in chloroplasts, cytoplasm and nucleus. In addition, a total of 12 sequence motifs were extracted from all identified K_hib peptides, and a basic amino acid residue (K), an acidic amino acid residue (E) and three aliphatic amino acid residues with small side chains (G/A/V) were found to be more preferred around the K_hib site. Furthermore, 16 highly-connected clusters of K_hib proteins were retrieved from the global PPI network, which suggest that K_hib modifications tend to occur in proteins associated with specific functional clusters.

CONCLUSIONS

These findings suggest that K_hib modification is an abundant and conserved PTM in soybean and that this modification may play an important role in regulating physiological processes in soybean leaves. The K_hib proteomic data obtained in this study will help to further elucidate the regulatory mechanisms of K_hib modification in soybean in the future.

Current perspectives of ubiquitination and SUMOylation in abiotic stress tolerance in plants

Post-translational modification (PTM) is a critical and rapid mechanism to regulate all the major cellular processes through the modification of diverse protein substrates. Substrate-specific covalent attachment of ubiquitin and Small Ubiquitin-Like Modifier (SUMO) with the target proteins, known as ubiquitination and SUMOylation, respectively, are crucial PTMs that regulate almost every process in the cell by modulating the stability and fidelity of the proteins. Ubiquitination and SUMOylation play a very significant role to provide tolerance to the plants in adverse environmental conditions by activating/deactivating the pre-existing proteins to a great extent. We reviewed the importance of ubiquitination and SUMOylation in plants, implicating its prospects in various abiotic stress regulations. An exhaustive study of molecular mechanisms of ubiquitination and SUMOylation of plant proteins and their role will contribute to the understanding of physiology underlying mitigation of the abiotic stresses and survival in plants. It will be helpful to strategize the improvement of crops for abiotic stress tolerance.