Exploring the molecular foundation of the gene-regulatory systems underlying agronomic parameters or/and plant responses to both abiotic and biotic stresses is crucial for crop improvement. Thus, transcription factors, which alone or in combination directly regulated the targeted gene expression levels, are appropriate players for enlightening agronomic parameters through genetic engineering. In this regard, homeodomain leucine zipper (HD-ZIP) genes family concerned with enlightening plant growth and tolerance to environmental stresses are considered key players for crop improvement. This gene family containing HD and LZ domain belongs to the homeobox superfamily. It is further classified into four subfamilies, namely HD-ZIP I, HD-ZIP II, HD-ZIP III, and HD-ZIP IV. The first HD domain-containing gene was discovered in maize cells almost three decades ago. Since then, with advanced technologies, these genes were functionally characterized for their distinct roles in overall plant growth and development under adverse environmental conditions. This review summarized the different functions of HD-ZIP genes in plant growth and physiological-related activities from germination to fruit development. Additionally, the HD-ZIP genes also respond to various abiotic and biotic environmental stimuli by regulating defense response of plants. This review, therefore, highlighted the various significant aspects of this important gene family based on the recent findings. The practical application of HD-ZIP biomolecules in developing bioengineered plants will not only mitigate the negative effects of environmental stresses but also increase the overall production of crop plants.

Melaleuca is one of the genera of the Myrtaceae family enriched in tea tree oil (TTO). Tea tree oils of Melaleuca bracteata and Melaleuca alternifolia are of prime importance and have antioxidant and antimicrobial properties. Terpinen-4-ol and 1-8 cineole are major constituents of M. alternifolia oil. The percentages of the compounds in the oils can slightly vary according to the region of plant harvest, the distillation technique, or the part of the plant used for oil extraction. TTO has a bactericidal effect against various bacterial species such as Bacillus cereus, B. subtilis, E. coli, Pseudomonas putida, and S. aureus. Several reports proved that this essential oil is also effective against fungal strains of Fusarium, Aspergillus, and Candida species. It also has antioxidant properties such as radical scavenging activity and reducing power. The antioxidant properties of TTO at a concentration of 30 mM were observed to be greater than those of butylated hydroxytoluene (BHT), commonly used as a synthetic antioxidant. TTO is also an effective organic fungicide, herbicide, and insecticide for use in the agriculture sector. Postharvest application of the oil has been found efficient on sweet basil, citrus, and strawberry. It is concluded that tea tree oil has the potential to be used in the food, agriculture, and pharmaceutical industries as a natural antimicrobial and preservative agent. This review provides comprehensive information regarding the antioxidant and antimicrobial activities of tea tree oil and its potential applications in agriculture.

Heavy metal stress, including from chromium, has detrimental effects on crop growth and yields worldwide. Plant growth-promoting rhizobacteria (PGPR) have demonstrated great efficiency in mitigating these adverse effects. The present study investigated the potential of the PGPR strain Azospirillum brasilense EMCC1454 as a useful bio-inoculant for boosting the growth, performance and chromium stress tolerance of chickpea (Cicer arietinum L.) plants exposed to varying levels of chromium stress (0, 130 and 260 µM K₂Cr₂O₇). The results revealed that A. brasilense EMCC1454 could tolerate chromium stress up to 260 µM and exhibited various plant growth-promoting (PGP) activities, including nitrogen fixation, phosphate solubilization, and generation of siderophore, trehalose, exopolysaccharide, ACC deaminase, indole acetic acid, and hydrolytic enzymes. Chromium stress doses induced the formation of PGP substances and antioxidants in A. brasilense EMCC1454. In addition, plant growth experiments showed that chromium stress significantly inhibited the growth, minerals acquisition, leaf relative water content, biosynthesis of photosynthetic pigments, gas exchange traits, and levels of phenolics and flavonoids of chickpea plants. Contrarily, it increased the concentrations of proline, glycine betaine, soluble sugars, proteins, oxidative stress markers, and enzymatic (CAT, APX, SOD, and POD) and non-enzymatic (ascorbic acid and glutathione) antioxidants in plants. On the other hand, A. brasilense EMCC1454 application alleviated oxidative stress markers and significantly boosted the growth traits, gas exchange characteristics, nutrient acquisition, osmolyte formation, and enzymatic and non-enzymatic antioxidants in chromium-stressed plants. Moreover, this bacterial inoculation upregulated the expression of genes related to stress tolerance (CAT, SOD, APX, CHS, DREB2A, CHI, and PAL). Overall, the current study demonstrated the effectiveness of A. brasilense EMCC1454 in enhancing plant growth and mitigating chromium toxicity impacts on chickpea plants grown under chromium stress circumstances by modulating the antioxidant machinery, photosynthesis, osmolyte production, and stress-related gene expression.

Human activities all over the world cause many changes in the environment. These changes resulted in more complicated challenges facing all living things on earth. Among these challenges are abiotic stresses, particularly salinity and drought, which contribute to the huge crops yield loss around the world, thereby leading to food insecurity issues. Plants combat these adverse abiotic stress impacts via evolving a variety of physiological, biochemical and molecular mechanisms. Tremendous promising techniques are being used to enhance plant abiotic stress tolerance, including the applications of nanoparticles, which are thought to enhance plant performance under stress conditions. Nanoparticles are being used to deliver nutrients to plants, overcome plant diseases and pathogens and to sense and monitor trace elements present in soil. In this review, a glimpse of how nanoparticles could mitigate the negative impacts of salinity or drought stress on plants at the physiological, biochemical and molecular levels is elucidated and discussed. Understanding the underlying mechanisms of nanoparticles in abiotic stress tolerance will open the doors for further improvements in the yield, production and quality of main crops facing the changing environmental challenges.

Wheat (Triticum aestivum L.) is a key food crop, accounting for approximately 765 million tons produced worldwide. The present study evaluated 16 wheat genotypes using 19 morphological and phenological traits, 16 molecular markers (Inter Simple Sequence Repeats and Start Codon Targeted; ISSR and SCoT) and rbcL and matK plastid gene barcoding. The 16 wheat genotypes showed significant genetic variation using the markers assayed. Cell plot of phenological parameters revealed significant differences among the 16-day-old seedlings of wheat genotypes at Z1.1 growth stage. Collectively, W2 genotype had the lowest shoot length (SL), length of first internodes (LFI) and leaf area (LA) values, while W8 genotype had the highest diameter of first internode (DFI) and LA values. Furthermore, W7 genotype had the maximum plant biomass (PB) and leaf width (LW) values. Geometric models grouped wheat kernels into “rounded” and “nearly elongated”. Estimates of heritability (H²) for these morphological characters ranged from 4.93 to 100%. The highest H² values were recorded for root number (RN) (100%) followed by SL (88.72%), LFI (88.30%), LA (87.76%) and Feret diameter (86.68%), while the lowest H² value was recorded for DFI (4.93%). Furthermore, highly significant genotypic and phenotypic correlations were also observed among those traits. Reproducible fingerprinting profiles and high levels of polymorphism (PPB%) of SCoT (95.46%) and ISSR (82.41%) were recorded, indicating that they are effective tools for detecting genetic variation levels among wheat genotypes. The informativeness of markers were measured through estimation of polymorphic information content (PIC), resolving power (RP) and marker index (MI). The RP and PPB% of SCoT were significantly higher compared to those of ISSR. Comparatively, the two molecular markers were effective for studying genetic diversity among wheat genotypes, but SCoT markers were more informative. Moreover, based on the two chloroplast DNA regions (rbcL and matK), MatK was found to be more reliable for differentiating among T. aestivum genotypes. Taken together, using all the studied attributes, a clear taxonomic relationship can be used to identify T. aestivum species and improve their pragmatic production and development.

Arsenic (As) is one of the toxic heavy metal pollutants found in the environment. An excess of As poses serious threats to plants and diminishes their growth and productivity. NAC transcription factors revealed a pivotal role in enhancing crops tolerance to different environmental stresses. The present study investigated, for the first time, the functional role of SNAC3 in boosting As stress tolerance and grain productivity in rice (Oryza sativa L.). Two SNAC3-overexpressing (SNAC3-OX) and two SNAC3-RNAi transgenic lines were created and validated. The wild-type and transgenic rice plants were exposed to different As stress levels (0, 25, and 50 µM). The results revealed that SNAC3 overexpression significantly improved rice tolerance to As stress and boosted grain yield traits. Under both levels of As stress (25 and 50 µM), SNAC3-OX rice lines exhibited significantly lower levels of oxidative stress biomarkers and OsCRY1b (cryptochrome 1b) expression, but they revealed increased levels of gas exchange characters, chlorophyll, osmolytes (soluble sugars, proteins, proline, phenols, and flavonoids), antioxidant enzymes (SOD, CAT, APX, and POD), and stress-tolerant genes expression (OsSOD-Cu/Zn, OsCATA, OsCATB, OsAPX2, OsLEA3, OsDREB2B, OsDREB2A, OsSNAC2, and OsSNAC1) in comparison to wild-type plants. By contrast, SNAC3 suppression (RNAi) reduced grain yield components and reversed the aforementioned measured physio-biochemical and molecular traits. Taken together, this study is the first to demonstrate that SNAC3 plays a vital role in boosting As stress resistance and grain productivity in rice through modulating antioxidants, photosynthesis, osmolyte accumulation, and stress-related genes expression, and may be a useful candidate for further genetic enhancement of stress resistance in many crops.