Zakirullah Khan

Drought severely limits plant productivity, and understanding its regulatory mechanisms remains essential. Here, we characterize Lipid Transport Superfamily-Polyketide cyclase/dehydrase (LTS-PYL), a PYR/PYL/RCAR-domain gene, using Arabidopsis overexpression and CRISPR-Cas9 genome-edited lines to elucidate its role in drought adaptation. LTS-PYL overexpression enhanced early seedling growth, increasing root length (RL) by 40% and 31%, whereas genome-edited lines exhibited severe defects, including 42%, 28% reductions in fresh weight and 63%, 50% decreases in root length relative to WT-T. Under drought stress, overexpression lines displayed strong growth and reproductive resilience, with shoot length (SL) increased by up to 80%, silique length (Sil L) by 61%, and seed number doubled compared with WT-T. In contrast, genome-edited lines showed marked reductions in these traits, confirming their drought sensitivity. LTS-PYL overexpression strongly suppressed oxidative stress, reducing H₂O₂ by 74% and 68% and O₂⁻· by 39% and 38%, while increasing relative water content (RWC) by 42% and 39%. Genome-edited lines exhibited elevated (H₂O₂, O₂⁻·) and up to 33% lower RWC. Antioxidant capacity was also strengthened in overexpression plants, with catalase (CAT) and peroxidase (POD) activities increasing by 138%, 168% and 62%, 148%, and malondialdehyde (MDA) and electrolyte leakage (EL) reduced by 23%, 37%, relative to WT-T. Conversely, genome-edited lines showed weakened antioxidant defenses and higher membrane damage. Transcriptionally, overexpression activated drought-responsive genes, elevating LTS-PYL (604%, 472%), DREB2A (227%, 200%), and ABA levels (48%, 34%), whereas genome-edited lines showed strongly reduced expression and ABA decreases of 66%, 62%. Additionally, LTS-PYL enhanced osmotic adjustment, increasing proline (58%, 53%), sugars (37%, 46%), and sucrose (111%, 100%), while limiting chlorophyll (Chl) loss to 9%, 20%. Genome-edited lines exhibited reduced osmolytes and severe chlorophyll decline. Overall, LTS-PYL acts as a strong positive regulator of drought tolerance, integrating ABA signaling, osmotic adjustment, ROS detoxification, and transcriptional activation.

Studying hypoxia in rice is particularly important because oxygen deficiency during germination severely limits seedling establishment. Understanding the molecular and physiological mechanisms underlying hypoxic tolerance is therefore crucial for improving rice yield stability under flooded or waterlogged conditions. Progress in developing rice cultivars that thrive under flooding and low oxygen (hypoxic) conditions has been limited over the past two decades due to a lack of tolerant plant varieties and a limited understanding of genetic mechanisms. This study evaluated hypoxia tolerance in the Cheongcheong Nagdong Double Haploid (CNDH) rice population, along with their parent lines, for hypoxia tolerance. Significant phenotypic differences were identified, with the Cheongcheong and CNDH lines CNDH13, CNDH35, and CNDH91 showing strong hypoxia tolerance, while Nagdong and CNDH lines CNDH14-2, CNDH43, and CNDH50-1 were susceptible to hypoxia. Root length was unaffected by hypoxia, while shoot length and fresh weight were key tolerance indicators. Comprehensive quantitative trait loci (QTL) analysis based on logarithm of the odds (LOD) scores above 3.0 identified three QTLs associated with hypoxia tolerance, indicating significant genetic control: qSL-8 and qSL-10 (shoot length) and qFW-2 (fresh weight). The gene expression analysis performed under hypoxic conditions highlighted that 35 candidate genes within these QTL regions exhibited differential regulation: Os02g0184200, Os08g0430200, Os08g0431900, and Os08g0432500 were upregulated, whereas Os08g0439100, Os10g0343400, Os10g0395400, and Os10g0405600 were downregulated in both resistant and susceptible lines. Os08g0431900 displayed significant expression changes correlating with hypoxia resistance. Phylogenetic and protein–protein interaction analyses revealed that Os08g0431900 is highly conserved and interacts with proteins involved in stress responses, suggesting that these proteins are crucial in hypoxia tolerance. These findings provide valuable insights into the genetic basis of hypoxia tolerance and identify key genes for future breeding programs to develop hypoxia-resistant rice varieties.

Progress in developing rice cultivars that thrive under flooding and low oxygen (hypoxic) conditions has been limited over the past two decades due to a lack of tolerant plant varieties and a limited understanding of genetic mechanisms. This study evaluated hypoxia tolerance in the Cheongcheong Nagdong Double Haploid (CNDH) rice population, along with their parent lines, for hypoxia tolerance. Significant phenotypic differences were identified, with the Cheongcheong and CNDH lines CNDH13, CNDH35, and CNDH91 showing strong hypoxia tolerance, while Nagdong and CNDH lines CNDH14-2, CNDH43, and CNDH50-1 were susceptible to hypoxia. Root length was unaffected by hypoxia, while shoot length and fresh weight were key tolerance indicators. Comprehensive quantitative trait loci (QTL) analysis based on logarithm of the odds (LOD) scores above 3.0 identified three QTLs associated with hypoxia tolerance, indicating significant genetic control: qSL-8 and qSL-10 (shoot length) and qFW-2 (fresh weight). The gene expression analysis performed under hypoxic conditions highlighted that 35 candidate genes within these QTL regions exhibited differential regulation: Os02g0184200, Os08g0430200, Os08g0431900, and Os08g0432500 were upregulated, whereas Os08g0439100, Os10g0343400, Os10g0395400, and Os10g0405600 were downregulated in both resistant and susceptible lines. Os08g0431900 displayed significant expression changes correlating with hypoxia resistance. Phylogenetic and protein–protein interaction analyses revealed that Os08g0431900 is highly conserved and interacts with proteins involved in stress responses, suggesting that these proteins are crucial in hypoxia tolerance. These findings provide valuable insights into the genetic basis of hypoxia tolerance and identify key genes for future breeding programs to develop hypoxia-resistant rice varieties.

This study investigates the impact of exogenous calcium and gamma-aminobutyric acid (GABA) supplementation on rice growth and stress tolerance under white-backed planthopper (WBPH) infestation. We evaluated several phenotypic traits, including shoot/root length, leaf width, tiller number, panicle length, and relative water content, alongside physiological markers such as oxidative stress indicators, antioxidant enzymes activities, hormonal levels, and amino acids biosynthesis. Our results indicate that WBPH stress significantly reduces growth parameters but calcium and GABA supplementation markedly enhance shoot length (by 26% and 36%) and root length (by 38% and 64%), respectively, compared to WBPH-infested plants. Both supplementations also reduced oxidative stress, as evidenced by decreased H₂O₂ and O₂^•− levels and a lower electrolyte leakage. Notably, calcium and GABA treatments increased antioxidant enzyme activities, with GABA boosting catalase (CAT) activity by 800%, peroxidase (POD) by 144%, and superoxide dismutase (SOD) by 62% under WBPH stress. Additionally, calcium and GABA enhanced the accumulation of stress hormones (abscisic acid ABA) and salicylic acid (SA) and promoted stomatal closure, contributing to improved water conservation. This study reveals that calcium regulates the GABA shunt pathway, significantly increasing GABA and succinate levels in both root and shoot. Furthermore, calcium and GABA supplementation enhance the biosynthesis of key amino acids and improve ion homeostasis, particularly elevating calcium (Ca), iron (Fe), and magnesium (Mg) levels under WBPH stress. Overall, this study highlights the potential of exogenous calcium and GABA as effective strategies for enhancing rice plant tolerance to WBPH infestation by modulating various physiological and biochemical mechanisms. Further research is warranted to fully elucidate the underlying mechanisms of action.

The importance of gamma-aminobutyric acid (GABA) in plants has been highlighted due to its critical role in mitigating metal toxicity, specifically countering the inhibitory effects of copper stress on rice plants. This study involved pre-treating rice plants with 1 mM GABA for one week, followed by exposure to varying concentrations of copper at 50 μM, 100 μM, and 200 μM. Under copper stress, particularly at 100 μM and 200 μM, plant height, biomass, chlorophyll content, relative water content, mineral content, and antioxidant activity decreased significantly compared to control conditions. However, GABA treatment significantly alleviated the adverse effects of copper stress. It increased plant height by 13%, 18%, and 32%; plant biomass by 28%, 52%, and 60%; chlorophyll content by 12%, 30%, and 24%; and relative water content by 10%, 24%, and 26% in comparison to the C50, C100, and C200 treatments. Furthermore, GABA treatment effectively reduced electrolyte leakage by 11%, 34%, and 39%, and the concentration of reactive oxygen species, such as malondialdehyde (MDA), by 9%, 22%, and 27%, hydrogen peroxide (H₂O₂) by 12%, 38%, and 30%, and superoxide anion content by 8%, 33, and 39% in comparison to C50, C100, and C200 treatments. Additionally, GABA supplementation led to elevated levels of glutathione by 69% and 80%, superoxide dismutase by 22% and 125%, ascorbate peroxidase by 12% and 125%, and catalase by 75% and 100% in the C100+G and C200+G groups as compared to the C100 and C200 treatments. Similarly, GABA application upregulated the expression of GABA shunt pathway-related genes, including gamma-aminobutyric transaminase (OsGABA-T) by 38% and 80% and succinic semialdehyde dehydrogenase (OsSSADH) by 60% and 94% in the C100+G and C200+G groups, respectively, as compared to the C100 and C200 treatments. Conversely, the expression of gamma-aminobutyric acid dehydrogenase (OsGAD) was downregulated. GABA application reduced the absorption of Cu²⁺ by 54% and 47% in C100+G and C200+G groups as compared to C100, and C200 treatments. Moreover, GABA treatment enhanced the uptake of Ca²⁺ by 26% and 82%, Mg²⁺ by 12% and 67%, and K⁺ by 28% and 128% in the C100+G and C200+G groups as compared to C100, and C200 treatments. These findings underscore the pivotal role of GABA-induced enhancements in various physiological and molecular processes, such as plant growth, chlorophyll content, water content, antioxidant capacity, gene regulation, mineral uptake, and copper sequestration, in enhancing plant tolerance to copper stress. Such mechanistic insights offer promising implications for the advancement of safe and sustainable food production practices.