Genetic and biochemical studies on some Egyptian wheat genotypes under drought stress

Background Strategic crops need to be screened from time to time to select the most tolerant and stable genotypes incompatible with environmental conditions. This research experiments were carried out to screen thirteen Egyptian wheat genotypes under water regime stress to select the most tolerant genotypes to drought conditions in two successive seasons. The studied genotypes were cultivated in rows, and the irrigation duration period between any two successive irrigations was elongated to double period to supply these genotypes with only 50% of the water needed in well watering conditions. This evaluation concerned on some yield production indexes such as spike weight, spike length, spike number, grains number/spike the 100 grains weight and stress susceptibility index and the cytogenetic evaluation index of the pollen grains viability on two successive seasons (2017–2018 and 2018–2019). This screening also carried out some biochemical and molecular analysis on the wheat genotypes at the seedling stage by the end of 2018 (the first season of water regime) targeting total protein profile, proline amino acid accumulation and Betaine aldehyde dehydrogenase-1 enzyme gene expression via semiquantitative RT-PCR. Results Sids 12 genotype recorded the highest SW, SL and SN. Considering the number of grains/plant and the number of spikes/plant are the principal yield components, and 100 grains weight is the principal yield quality, Sids 12 also declared its tolerance to water regime on regarding the plant productivity to grains’ number/plant and scored the lowest SSI. Pollen viability and protein profile were also affected as a response to the water regime. Proline concentration in fresh leaves emphasizes the tolerance of Sids 12, Misr 2 and Gemmieza 9 genotypes to the water deficit. Conclusion Among the examined genotypes, Sids 12, Misr 2, Shandaweel1 and Gemmieza 9 and line 20 are recommended to be cultivated in water shortage conditions as they show high performance under water regime conditions.

Haplotype Analysis of BADH1 by Next-Generation Sequencing Reveals Association with Salt Tolerance in Rice during Domestication

Betaine aldehyde dehydrogenase 1 (BADH1), a paralog of the fragrance gene BADH2, is known to be associated with salt stress through the accumulation of synthesized glycine betaine (GB), which is involved in the response to abiotic stresses. Despite the unclear association between BADH1 and salt stress, we observed the responses of eight phenotypic characteristics (germination percentage (GP), germination energy (GE), germination index (GI), mean germination time (MGT), germination rate (GR), shoot length (SL), root length (RL), and total dry weight (TDW)) to salt stress during the germination stage of 475 rice accessions to investigate their association with BADH1 haplotypes. We found a total of 116 SNPs and 77 InDels in the whole BADH1 gene region, representing 39 haplotypes. Twenty-nine haplotypes representing 27 mutated alleles (two InDels and 25 SNPs) were highly (p < 0.05) associated with salt stress, including the five SNPs that have been previously reported to be associated with salt tolerance. We observed three predominant haplotypes associated with salt tolerance, Hap_2, Hap_18, and Hap_23, which were Indica specific, indicating a comparatively high number of rice accessions among the associated haplotypes. Eight plant parameters (phenotypes) also showed clear responses to salt stress, and except for MGT (mean germination time), all were positively correlated with each other. Different signatures of domestication for BADH1 were detected in cultivated rice by identifying the highest and lowest Tajima’s D values of two major cultivated ecotypes (Temperate Japonica and Indica). Our findings on these significant associations and BADH1 evolution to plant traits can be useful for future research development related to its gene expression.

The Determination of Aromatic Character of Several Local Rice Varieties using Phenotypic Analysis and Molecular DNA

The pandan scent in aromatic rice has been known as the result of 8 bp deletions and 3 Single Nucleotide Polymorphisms (SNPS) in BADH2 gene, which produce non-functional betaine aldehyde dehydrogenase (BADH) enzyme. Several DNA markers for aromatic character based on mutation in BADH2 gene have been developed. In our experiment, we analysed the presence of aromatic character in four local rice variety such as Merah Wangi, Pendok, Genjah Arum, and Mentik Wangi Susu using KOH method and DNA molecular method using three DNA markers to detect mutation that responsible for the development of aromatic character. Phenotype analysis using KOH method showed that Merah Wangi, Genjah Arum, and Mentik Wangi Susu produce pandan scents. PCR analysis using Bradbury and Badex7-5, and RM223 markers showed the presence of BADH2 mutation in Merah Wangi and Mentik Wangi Susu, whereas Pendok and Genjah Arum did not show BADH2 mutation using those used three markers. Our results indicate that among four investigated local rice, only Merah Wangi and Mentik Wangi Susu are categorized as aromatic rice whereas Pendok and Genjah Arum are non-aromatic.Keywords: genetic analysis, aromatic rice, specific markers, genetic mutation.

Fragrance in Pandanus amaryllifoliusRoxb. Despite the Presence of a Betaine Aldehyde Dehydrogenase 2

Pandanus amaryllifoliusRoxb. accumulates the highest concentration of the major basmati aroma volatile 2-acetyl-1-pyrroline (2AP) in the plant kingdom. The expression of 2AP is correlated with the presence of a nonfunctional betaine aldehyde dehydrogenase 2(BADH2) in aromatic rice and other plant species. In the present study, a full-length BADH2 sequence was reconstructed from the transcriptome data of leaf tissue from P. amaryllifolius seedlings. Based on this sequence, a 1509 bp coding sequence was defined that encoded a 54 kD PaBADH2protein. This revealed the presence of a full-length BADH2 protein in P. amaryllifolius. Moreover, quantitative real-time PCR analysis, combined with BADH2 enzyme activity, confirmed the expression and functionality of the PaBADH2 protein. To understand the apparent structural variation, docking analysis was carried out in which protein showed a good affinity with both betaine aldehyde (BAD) and γ-aminobutyraldehyde (GAB-ald) as substrates. Overall, the analysis showed the presence of a functional BADH2, along with substantial 2AP synthesis (4.38 ppm). Therefore, we conclude that unlike all other plants studied to date, 2AP biosynthesis in P. amaryllifolius is not due to the inactivation of BADH2.

Heat Priming of Lentil (Lens culinaris Medik.) Seeds and Foliar Treatment with γ-Aminobutyric Acid (GABA), Confers Protection to Reproductive Function and Yield Traits under High-Temperature Stress Environments

Gradually increasing temperatures at global and local scales are causing heat stress for cool and summer-season food legumes, such as lentil (Lens culinaris Medik.), which is highly susceptible to heat stress, especially during its reproductive stages of development. Hence, suitable strategies are needed to develop heat tolerance in this legume. In the present study, we tested the effectiveness of heat priming (HPr; 6 h at 35 °C) the lentil seeds and a foliar treatment of γ-aminobutyric acid (GABA; 1 mM; applied twice at different times), singly or in combination (HPr+GABA), under heat stress (32/20 °C) in two heat-tolerant (HT; IG2507, IG3263) and two heat-sensitive (HS; IG2821, IG2849) genotypes to mitigate heat stress. The three treatments significantly reduced heat injury to leaves and flowers, particularly when applied in combination, including leaf damage assessed as membrane injury, cellular oxidizing ability, leaf water status, and stomatal conductance. The combined HPr+GABA treatment significantly improved the photosynthetic function, measured as photosynthetic efficiency, chlorophyll concentration, and sucrose synthesis; and significantly reduced the oxidative damage, which was associated with a marked up-regulation in the activities of enzymatic antioxidants. The combined treatment also facilitated the synthesis of osmolytes, such as proline and glycine betaine, by upregulating the expression of their biosynthesizing enzymes (pyrroline-5-carboxylate synthase; betaine aldehyde dehydrogenase) under heat stress. The HPr+GABA treatment caused a considerable enhancement in endogenous levels of GABA in leaves, more so in the two heat-sensitive genotypes. The reproductive function, measured as germination and viability of pollen grains, receptivity of stigma, and viability of ovules, was significantly improved with combined treatment, resulting in enhanced pod number (21–23% in HT and 35–38% in HS genotypes, compared to heat stress alone) and seed yield per plant (22–24% in HT and 37–40% in HS genotypes, in comparison to heat stress alone). The combined treatment (HPr+GABA) was more effective and pronounced in heat-sensitive than heat-tolerant genotypes for all the traits tested. This study offers a potential solution for tackling and protecting heat stress injury in lentil plants.

Lanthanum (La) improves growth, yield formation and 2-acetyl-1-pyrroline biosynthesis in aromatic rice (Oryza sativa L.)

Background Lanthanum (La) is a rare earth element that can influence plant growth and development. However, the effect of La on growth, yield formation and 2-acetyl-1-pyrroline (2-AP, a key compound responsible for the aroma of rice) biosynthesis in aromatic rice (Oryza sativa L. subsp. japonica Kato) has not been reported. Therefore, the present study investigated the effects of La on growth, photosynthesis, yield formation and 2-AP biosynthesis in aromatic rice through three experiments. Results Two pot experiments and a two-year field trial were conducted with different rates of La application (20–120 LaCl3 mg kg−1 and 12 kg ha−1 LaCl3), and treatments without La application were used as controls. The results showed that the application of LaCl3 at 80 and 100 mg kg−1 and at 12 kg ha−1 greatly increased the 2-AP content (by 6.45–43.03%) in aromatic rice seedlings and mature grains compared with the control. The La treatments also increased the chlorophyll content, net photosynthetic rate and total aboveground biomass of rice seedlings. Higher antioxidant enzyme (superoxide, peroxidase, and catalase) activity was detected in the La treatments than in the control. The La treatments also increased the grain yield, grain number per panicle and seed-setting rate of aromatic rice relative to the control. Moreover, the grain proline and γ-aminobutyric acid contents and the activity of betaine aldehyde dehydrogenase significantly decreased under the La treatment. The application of La to soil enhanced the activity of proline dehydrogenase by 20.62–56.95%. Conclusions La improved the growth, yield formation and 2-AP content of aromatic rice and enhanced 2-AP biosynthesis by increasing the conversion of proline to 2-AP and decreasing the conversion of GABald to GABA.

Betaine Aldehyde Dehydrogenase (BADH) vs. Flavodoxin (Fld): Two Important Genes for Enhancing Plants Stress Tolerance and Productivity

Abiotic stresses, mainly salinity and drought, are the most important environmental threats that constrain worldwide food security by hampering plant growth and productivity. Plants cope with the adverse effects of these stresses by implementing a series of morpho-physio-biochemical adaptation mechanisms. Accumulating effective osmo-protectants, such as proline and glycine betaine (GB), is one of the important plant stress tolerance strategies. These osmolytes can trigger plant stress tolerance mechanisms, which include stress signal transduction, activating resistance genes, increasing levels of enzymatic and non-enzymatic antioxidants, protecting cell osmotic pressure, enhancing cell membrane integrity, as well as protecting their photosynthetic apparatus, especially the photosystem II (PSII) complex. Genetic engineering, as one of the most important plant biotechnology methods, helps to expedite the development of stress-tolerant plants by introducing the key tolerance genes involved in the biosynthetic pathways of osmolytes into plants. Betaine aldehyde dehydrogenase (BADH) is one of the important genes involved in the biosynthetic pathway of GB, and its introduction has led to an increased tolerance to a variety of abiotic stresses in different plant species. Replacing down-regulated ferredoxin at the acceptor side of photosystem I (PSI) with its isofunctional counterpart electron carrier (flavodoxin) is another applicable strategy to strengthen the photosynthetic apparatus of plants under stressful conditions. Heterologous expression of microbially-sourced flavodoxin (Fld) in higher plants compensates for the deficiency of ferredoxin expression and enhances their stress tolerance. BADH and Fld are multifunctional transgenes that increase the stress tolerance of different plant species and maintain their production under stressful situations by protecting and enhancing their photosynthetic apparatus. In addition to increasing stress tolerance, both BADH and Fld genes can improve the productivity, symbiotic performance, and longevity of plants. Because of the multigenic and complex nature of abiotic stresses, the concomitant delivery of BADH and Fld transgenes can lead to more satisfying results in desired plants, as these two genes enhance plant stress tolerance through different mechanisms, and their cumulative effect can be much more beneficial than their individual ones. The importance of BADH and Fld genes in enhancing plant productivity under stress conditions has been discussed in detail in the present review.