Ibrahim Khan

Main conclusion This work highlights pollen thermotolerance as vital for reproductive success under heat stress, integrating molecular regulation, gene mapping, and breeding strategies to accelerate development of resilient, high-yielding crop varieties. Abstract Bulliform cells are specialized epidermal motor cells predominantly found on the adaxial surface of grass leaves and play a crucial role in mediating adaptive leaf rolling under water deficit conditions. This dynamic morphophysiological response reduces the exposed surface area, minimizes transpirational water loss, and creates favorable microclimatic conditions for photosynthetic tissues, thereby enhancing drought tolerance. This review highlights molecular regulation as a central component of bulliform cell function and integrates it with morphological, anatomical, physiological, and hormonal responses. Recent studies have identified genetic and hormonal regulators of bulliform cell development, including key transcription factors such as SRL1, ROC1, ACL1/2, as well as phytohormones including abscisic acid (ABA), cytokinins (CKs), and brassinosteroids (BRs), revealing a complex integration of developmental and stress-responsive pathways. Advances in high-resolution imaging, single-cell transcriptomics, and machine learning provide mechanistic insights into bulliform cell-specific gene expression, turgor dynamics, and structural contributions to leaf rolling. Quantitative analyses, including genome-wide association studies (GWAS) and quantitative trait locus (QTL) mapping, have associated BC traits with leaf rolling indices, water-use efficiency, and drought tolerance in cereals. Despite these advances, significant knowledge gaps remain, particularly regarding how bulliform cells respond to combined abiotic stresses and the physiological trade-offs between water conservation and leaf thermoregulation. This review presents a novel, integrative framework of multi-omics, systems biology, and AI-driven modeling to develop predictive insights into bulliform cell behavior to optimize their anatomical and physiological traits for enhanced crop resilience. In addition, this review integrates current anatomical, physiological, genetic, and computational insights into bulliform cells, revealing their pivotal role in plant adaptation and their emerging potential as targets for developing stress-resilient crops.

Calcium ions (Ca ²⁺ ) are essential for plant development and stress responses, including heavy metal (HM) stress. However, the roles and mechanisms of calmodulin proteins ( SlCalMs ) in mediating cadmium (Cd) stress in Solanum lycopersicum , a model crop, remain poorly understood. This study aimed to investigate the calcium‐mediated stress response in S. lycopersicum by identifying and characterizing the SlCalMs gene family, a key subfamily of calcium‐binding proteins ( CBPs ), to elucidate their potential roles in stress tolerance. A genome‐wide identification of SlCalMs was conducted using Oryza sativa sequences as a reference. Bioinformatics analyses included BLASTP searches, sequence alignment, phylogenetics, assessment of physicochemical properties, gene structure and motif analysis, chromosomal mapping and duplication events. Gene expression was assessed under Cd stress using RNA‐seq and validated by quantitative real‐time polymerase chain reaction (qRT‐PCR). Molecular docking simulations evaluated Cd‐binding affinities, and protein–protein interaction networks, and Gene Ontology (GO) enrichment were used to explore biological functions. Eight distinct SlCalM groups were identified, varying in gene size, exon number and isoelectric point. Conserved motifs, exon–intron patterns and stress‐responsive cis‐elements were identified. Chromosomal analysis revealed segmental duplications. Under Cd stress, several SlCalMs showed differential expression; notably, Solyc04g077830 was significantly downregulated and showed strong Cd‐binding affinity in silico , suggesting a role in Cd sequestration. GO and interaction network analyses confirmed their involvement in Ca ²⁺ signalling, metal ion binding and stress‐related pathways. This study provides comprehensive insight into the structure, evolution and functional roles of SlCalMs in tomato. Their involvement in Ca ²⁺ signalling and Cd stress response highlights their potential for improving HM tolerance, offering valuable targets for future genetic or biotechnological interventions in crop improvement.

As a sustainable alternative to inorganic fertilisers, the combined application of plant‐growth promoting microbes and organic amendments offers an efficient biological approach to enhance plant growth under stress conditions. In this study, we present the complete genome sequence and functional annotation of the soil bacterial strain Priestia megaterium mj1212 (formerly classified as Bacillus megaterium), supporting its recent taxonomic reclassification and revealing its potential for secondary metabolites production, plant growth promotion, and adoption to environmental stresses. Our results showed that the combined application of N‐acetylglucosamine (GlcNAc) and mj1212 exhibited a synergistic effect, significantly increasing the length and weight of soybean shoots and roots by up to 24.36% and 42.22%, and 10.95% and 14.51%, respectively, under 150 mM NaCl stress. In addition, both sole and combined treatments of GlcNAc and mj1212 significantly enhanced root nodules formation, photosynthetic parameters, and relative water contents. Similarly, the individual and combined treatments of GlcNAc and mj1212 significantly increased polyphenol oxidase and flavonoid content, while reducing superoxide oxidase and catalase (CAT) activities. Organic acids analysis revealed increased levels of citric acids, and malic acids, while succinic acids and lactic acids levels decreased significantly under both conditions, with a slight antagonistic effect observed under stress. Notably, nitric oxide (SNO) levels, which decreased by 60.59% under NaCl stress, were restored by 492.55% of the stress level (nM/µg) with the combined treatment of GlcNAc and mj1212. The findings also suggested that GlcNAc and mj1212 treatments could improve soybean tolerance to salt stress by modulating abscisic acids biosynthesis. These findings underscore the potential of mj1212 and GlcNAc as effective biofertilizers for enhancing salt stress tolerance and promoting sustainable crop growth.

Agricultural productivity is adversely affected by soil salinization and contamination with heavy metals, emphasizing the necessity for environmentally friendly technologies. This study investigates the impact of sodium chloride (NaCl) and arsenic (As) stress on tomato seedlings and explores the stress-alleviating effects of mannitol and a halophilic bacterium, Nitratrieducator aquimarinus SPSB2. Our results revealed that bacteria strainSPSB2 establishes a symbiotic relationship with tomato plants, which modulates the secondary metabolites and antioxidant system in tomato plants exposed to both NaCl and As stress. Under the NaCl and As stress tomato seedling growth was significantly reduced, although this reduction was mitigated by bacteria strain SPSB2 and mannitol treatment. When exposed to NaCl stress, the bacterial strain enhances shoot and root length by 84.8% and 152.5%, respectively. Similarly, under the As stress conditions, bacteria strain SPSB2 inoculation increased the shoot and root weights by 63.1% and 45.5%, respectively. Bacteria strain SPSB2 inoculation also significantly enhanced the chlorophyll a, b, and carotenoid contents by 76.3%, 78%, and 50%, respectively, compared to their non-inoculated counterparts under As stress conditions. Furthermore, during NaCl and As stress conditions, treatments with SPSB2 and mannitol increase the levels of enzymatic components (catalase, polyphenol oxidases) and non-enzymatic components (flavonol protein, sugar, starch), indicating a stress-alleviating effect of bacteria strain SPSB2 and mannitol. In the current study, the bacteria strain SPSB2 was more effective than mannitol in improving tomato plants' salinity and heavy metal tolerance regarding growth and physiological attributes. The symbiotic relationship between SPSB2 and tomato plants positively impacted various parameters, including plant growth, chlorophyll content, and antioxidant system activity. Moreover, the study suggests that SPSB2 is more effective than mannitol in improving tomato plants' salinity and heavy metal tolerance. These findings contribute to the understanding of environmentally friendly strategies for managing soil salinization and heavy metal contamination in agriculture, and the potential use of SPSB2 in microbial-assisted phytoremediation of polluted saline soils.

Modern irrigation practices and industrial pollution can contribute to the simultaneous occurrence of salinity and heavy metal contamination in large areas of the world, resulting in significant negative effects on crop productivity and sustainability. This study aimed to investigate the growth-promoting potentials of an important endophytic fungal strain SL3 and to compare its potential with exogenous IAA (indole-3-acetic acid) in the context of salt and heavy metal stress. The strain was assessed for plant growth-promoting traits such as the production of indole-3-acetic acid, gibberellins (GA), and siderophore. We selected two important crops, mung bean and maize, and examined various physiological and biochemical characteristics under 300 mM NaCl and 2.5 mM Pb stress conditions, with and without the application of IAA and SL3. This study’s results demonstrated that both IAA and SL3 positively impacted the growth and development of plants under normal and stressed conditions. In NaCl and Pb-induced stress conditions, the growth of mung bean and maize plants was significantly reduced. However, the application of IAA and SL3 helped to alleviate stress, leading to a significant increase in shoot/root length and weight compared to IAA and SL3 non-treated plants. The results revealed that photosynthetic pigments, accumulation of catalase (CAT), phenolic contents, polyphenol oxidase, and flavanols are higher in the IAA and SL3-treated plants than in the non-inoculated plants. This study’s findings revealed that applying the SL3 fungal strain positively influenced various physiological and biochemical processes in tested plant species under normal and stress conditions of NaCl and Pb. These findings also suggested that SL3 could be a potential replacement for widely used IAA to promote plant growth by improving photosynthetic efficiency, reducing oxidative stress, and enhancing metabolic activities in plants, including mung and maize. Moreover, this study highlights that SL3 has synergistic effects with IAA in enhancing resilience to salt and heavy stress and offers a promising avenue for future agricultural applications in salt and heavy metal-affected regions.

Salinity stress is one of the major abiotic factors limiting crop yield in arid and semi-arid regions. Plant growth-promoting fungi can help plants thrive in stressful conditions. In this study, we isolated and characterized 26 halophilic fungi (endophytic, rhizospheric, and soil) from the coastal region of Muscat, Oman, for plant growth-promoting activities. About 16 out of 26 fungi were found to produce IAA, and about 11 isolates (MGRF1, MGRF2, GREF1, GREF2, TQRF4, TQRF5, TQRF5, TQRF6, TQRF7, TQRF8, TQRF2) out of 26 strains were found to significantly improve seed germination and seedling growth of wheat. To evaluate the effect of the above-selected strains on salt tolerance in wheat, we grew wheat seedlings in 150 mM, 300 mM NaCl and SW (100% seawater) treatments and inoculated them with the above strains. Our findings showed that fungal strains MGRF1, MGRF2, GREF2, and TQRF9 alleviate 150 mM salt stress and increase shoot length compared to their respective control plants. However, in 300 mM stressed plants, GREF1 and TQRF9 were observed to improve shoot length. Two strains, GREF2 and TQRF8, also promoted plant growth and reduced salt stress in SW-treated plants. Like shoot length, an analogous pattern was observed in root length, and different salt stressors such as 150 mM, 300 mM, and SW reduced root length by up to 4%, 7.5%, and 19.5%, respectively. Three strains, GREF1, TQRF7, and MGRF1, had higher catalase (CAT) levels, and similar results were observed in polyphenol oxidase (PPO), and GREF1 inoculation dramatically raised the PPO level in 150 mM salt stress. The fungal strains had varying effects, with some, such as GREF1, GREF2, and TQRF9, showing a significant increase in protein content as compared to their respective control plants. Under salinity stress, the expression of DREB2 and DREB6 genes was reduced. However, the WDREB2 gene, on the other hand, was shown to be highly elevated during salt stress conditions, whereas the opposite was observed in inoculated plants.