Genome-Wide Analyses of Calcium Sensors Reveal Their Involvement in Drought Stress Response and Storage Roots Deterioration after Harvest in Cassava

Genome-Wide Identification of the IQM Gene Family and Their Transcriptional Responses to Abiotic Stresses in Kiwifruit (Actinidia eriantha)

IQM is a plant-specific calcium-binding protein that plays a pivotal role in various aspects of plant growth response to stressors. We investigated the IQM gene family and its expression patterns under diverse abiotic stresses and conducted a comprehensive analysis and characterization of the AeIQMs, including protein structure, genomic location, phylogenetic relationships, gene expression profiles, salt tolerance, and expression patterns of this gene family under different abiotic stresses. Based on phylogenetic analysis, these 10 AeIQMs were classified into three distinct subfamilies (I-III). Analysis of the protein motifs revealed a considerable level of conservation among these AeIQM proteins within their respective subfamilies in kiwifruit. The genomic distribution of the 10 AeIQM genes spanned across eight chromosomes, where four pairs of IQM gene duplicates were associated with segmental duplication events. qRT-PCR analysis revealed diverse expression patterns of these AeIQM genes under different hormone treatments, and most AeIQMs showed inducibility by salt stress. Further investigations indicated that overexpression of AeIQMs in yeast significantly enhanced salt tolerance. These findings suggest that AeIQM genes might be involved in hormonal signal transduction and response to abiotic stress in Actinidia eriantha. In summary, this study provides valuable insights into the physiological functions of IQMs in kiwifruit.

Preharvest UV-C Hormesis Induces Key Genes Associated With Homeostasis, Growth and Defense in Lettuce Inoculated With Xanthomonas campestris pv. vitians

Preharvest application of hormetic doses of ultraviolet-C (UV-C) generates beneficial effects in plants. In this study, within 1 week, four UV-C treatments of 0.4 kJ/m2 were applied to 3-week-old lettuce seedlings. The leaves were inoculated with a virulent strain of Xanthomonas campestris pv. vitians (Xcv) 48 h after the last UV-C application. The extent of the disease was tracked over time and a transcriptomic analysis was performed on lettuce leaf samples. Samples of lettuce leaves, from both control and treated groups, were taken at two different times corresponding to T2, 48 h after the last UV-C treatment and T3, 24 h after inoculation (i.e., 72 h after the last UV-C treatment). A significant decrease in disease severity between the UV-C treated lettuce and the control was observed on days 4, 8, and 14 after pathogen inoculation. Data from the transcriptomic study revealed, that in response to the effect of UV-C alone and/or UV-C + Xcv, a total of 3828 genes were differentially regulated with fold change (|log2-FC|) > 1.5 and false discovery rate (FDR) < 0.05. Among these, of the 2270 genes of known function 1556 were upregulated and 714 were downregulated. A total of 10 candidate genes were verified by qPCR and were generally consistent with the transcriptomic results. The differentially expressed genes observed in lettuce under the conditions of the present study were associated with 14 different biological processes in the plant. These genes are involved in a series of metabolic pathways associated with the ability of lettuce treated with hormetic doses of UV-C to resume normal growth and to defend themselves against potential stressors. The results indicate that the hormetic dose of UV-C applied preharvest on lettuce in this study, can be considered as an eustress that does not interfere with the ability of the treated plants to carry on a set of key physiological processes namely: homeostasis, growth and defense.

Genome-Wide Analysis of the Apple CBL Family Reveals That Mdcbl10.1 Functions Positively in Modulating Apple Salt Tolerance

Abiotic stresses are increasingly harmful to crop yield and quality. Calcium and its signaling pathway play an important role in modulating plant stress tolerance. As specific Ca²⁺ sensors, calcineurin B-like (CBL) proteins play vital roles in plant stress response and calcium signaling. The CBL family has been identified in many plant species; however, the characterization of the CBL family and the functional study of apple MdCBL proteins in salt response have yet to be conducted in apple. In this study, 11 MdCBL genes were identified from the apple genome. The coding sequences of these MdCBL genes were cloned, and the gene structure and conserved motifs were analyzed in detail. The phylogenetic analysis indicated that these MdCBL proteins could be divided into four groups. The functional identification in Na⁺-sensitive yeast mutant showed that the overexpression of seven MdCBL genes could confer enhanced salt stress resistance in transgenic yeast. The function of MdCBL10.1 in regulating salt tolerance was also verified in cisgenic apple calli and apple plants. These results provided valuable insights for future research examining the function and mechanism of CBL proteins in regulating apple salt tolerance.

Physiological and proteomic analysis on long-term drought resistance of cassava (Manihot esculenta Crantz)

Drought stress is one of the potent abiotic stress limiting cassava (Manihot esculenta) yield globally, but studies addressing both physiological and proteomic responses that how cassava crops can adjust their growth and metabolism under drought conditions are lacking. Combining leaf physiological and proteomic characteristics strongly allied with drought tolerance should results in enhanced drought tolerance in cassava crop. Therefore, the aims of this study were to explore the plant physiological and proteomic mechanisms involved in drought adaptation in cassava. Xinxuan 048 (XX048) was exposed to well-watered control (CK, relative soil water content (RSWC) as 80 ± 5%), mild drought stress (LD, RSWC as 65 ± 5%), moderate drought stress (MD, RSWC as 50 ± 5%) and severe drought stress (SD, RSWC as 35 ± 5%) from 30 days after planting. Under drought stress conditions, cassava plant showed a substantial decline in plant height, stem diameter, leaf number, leaf water content, the ratio of free water content to bound water content of leaf (FW/BW), net photosynthetic rate (Pn), intercellular CO₂ concentration (Ci), stomatal conductance (Gs) and transpiration rate (Tr) compared with well watered plants. However, compared with control, leaf water content, SPAD value, cell membrane permeability, malondialdehyde (MDA), soluble sugar, protein proline content SOD and CAT activity were at peak under drought stress. The proteomic analysis revealed that among 3 339 identified proteins, drought stress increased and decreased abundance of 262 and 296 proteins, respectively, compared with control condition. These proteins were involved in carbohydrate energy metabolism, protein homeostasis, transcription, cell structure, cell membrane transport, signal transduction, stress and defense responses. These data not only provides a comprehensive dataset on overall proteomic changes in cassava leaves under drought stress, but also highlights the mechanisms by which euphorbiaceae plants can adapt to drought conditions.

The Late Embryogenesis Abundant Protein Family in Cassava (Manihot esculenta Crantz): Genome-Wide Characterization and Expression during Abiotic Stress

Late embryogenesis abundant (LEA) proteins, as a highly diverse group of polypeptides, play an important role in plant adaptation to abiotic stress; however, LEAs from cassava have not been studied in cassava. In this study, 26 LEA members were genome-wide identified from cassava, which were clustered into seven subfamily according to evolutionary relationship, protein motif, and gene structure analyses. Chromosomal location and duplication event analyses suggested that 26 MeLEAs distributed in 10 chromosomes and 11 MeLEA paralogues were subjected to purifying selection. Transcriptomic analysis showed the expression profiles of MeLEAs in different tissues of stem, leaves, and storage roots of three accessions. Comparative transcriptomic analysis revealed that the function of MeLEAs in response to drought may be differentiated in different accessions. Compared with the wild subspecies W14, more MeLEA genes were activated in cultivated varieties Arg7 and SC124 after drought treatment. Several MeLEA genes showed induction under various stresses and related signaling treatments. Taken together, this study demonstrates the transcriptional control of MeLEAs in tissue development and the responses to abiotic stress in cassava and identifies candidate genes for improving crop resistance to abiotic stress.