ORCID Profile
0000-0003-0221-518X
Current Organisations
King Abdullah University of Science and Technology (KAUST)
,
King Abdullah University of Science and Technology
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Publisher: Wiley
Date: 15-06-2023
DOI: 10.1111/WRE.12585
Abstract: The witchweed Striga hermonthica , an obligate and noxious root–parasitic plant, remains a persistent threat to cereal production and poses a great challenge to smallholder farmers in Sub‐Saharan Africa. Inducing suicidal germination of Striga seeds by applying strigolactone analogs is a promising strategy to deplete the Striga seed bank of infested soils. Nevertheless, there is a need to increase the efficiency and improve the applicability of this strategy, which may be achieved by testing further Striga germination stimulants. Herein, we explored the potential of cytokinins in inducing Striga seed germination. We investigated their activity as a suicidal germination agent along with fluridone that inhibits carotenoid biosynthesis and hence reduces abscisic acid formation and facilitates breaking of seed dormancy. Under lab conditions, application of fluridone (at 100 μM) or cytokinins (at 100 μM) showed 19% and 63% Striga germination, respectively, while combining different cytokinins with fluridone led to above 93% germination of treated seeds, with thidiazuron as the most active cytokinin. Using rice ( cv IAC‐165), we also show that co‐application of fluoridone and thidiazuron to Striga infested pots before planting the host led to up to 86%–100% reduction in Striga emergence. In summary, cytokinins, particularly thidiazuron, could be useful suicidal agents to induce Striga seed germination and ultimately deplete the seedbank in Striga‐infested regions.
Publisher: American Chemical Society (ACS)
Date: 05-06-2023
Publisher: Cold Spring Harbor Laboratory
Date: 07-07-2023
DOI: 10.1101/2023.07.06.548005
Abstract: Seeds of the root parasitic plant Striga hermonthica undergo a conditioning process under humid and warm environments before germinating in response to host-released stimulants, particularly strigolactones (SLs). The plant hormone abscisic acid (ABA) regulates different growth and developmental processes, and stress response however, its role during Striga seed germination and early interactions with host plants is under-investigated. Here, we show that ABA inhibited Striga seed germination and that hindering its biosynthesis induced conditioning and germination in unconditioned seeds, which was significantly enhanced by treatment with the SL analog rac -GR24. However, the inhibitory effect of ABA remarkably decreased during conditioning, confirming the loss of sensitivity towards ABA in later developmental stages. ABA measurement showed a significant reduction of its content during the early conditioning stage and a significant increase upon rac -GR24-triggered germination. We observed this increase also in released seed exudates, which was further confirmed by using the Arabidopsis ABA-reporter GUS marker line. Seed exudates of germinated seeds, containing elevated levels of ABA, impaired the germination of surrounding Striga seeds in vitro and promoted root growth of a rice host towards germinated Striga seeds. Application of ABA as a positive control caused similar effects, indicating its function in Striga/Striga and Striga/host communications. In summary, we show that ABA is an essential player during seed dormancy and germination processes in Striga and acts as a rhizospheric signal released by germinated parasitic seeds to provide a competitive advantage and support host infestation. The root parasitic plant Striga hermonthica is a severe threat to cereal’s yield, endangering global food security. Herein, we uncover a new role of the known plant hormone abscisic acid (ABA) as a rhizospheric signal released by germinated Striga seeds, allowing them to better compete with surrounding un-conditioned seeds and facilitating host infestation. Our findings can help in developing strategies to control this parasite and mitigate its negative impact on the food supply and income of smallholder farmers.
Publisher: Wiley
Date: 20-01-2023
DOI: 10.1111/TPJ.16095
Abstract: The enzyme DWARF27 (D27) catalyzes the reversible isomerization of all‐ trans ‐ into 9‐ cis ‐β‐carotene, initiating strigolactone (SL) biosynthesis. Genomes of higher plants encode two D27‐homologs, D27‐like1 and ‐like2, with unknown functions. Here, we investigated the enzymatic activity and biological function of the Arabidopsis D27‐like1. In vitro enzymatic assays and expression in Synechocystis sp. PCC6803 revealed an unreported 13‐ cis /15‐ cis /9‐ cis ‐ and a 9‐ cis /all‐ trans ‐β‐carotene isomerization. Although disruption of AtD27‐like1 did not cause SL deficiency phenotypes, overexpression of AtD27‐like1 in the d27 mutant restored the more‐branching phenotype, indicating a contribution of AtD27‐like1 to SL biosynthesis. Accordingly, generated d27 d27like1 double mutants showed a more pronounced branching phenotype compared to d27. The contribution of AtD27‐like1 to SL biosynthesis is likely a result of its formation of 9‐ cis ‐β‐carotene that was present at higher levels in AtD27‐like1 overexpressing lines. By contrast, AtD27‐like1 expression correlated negatively with the content of 9‐ cis ‐violaxanthin, a precursor of ABA, in shoots. Consistently, ABA levels were higher in shoots and also in dry seeds of the d27like1 and d27 d27like1 mutants. Transgenic lines expressing GUS driven by the AtD27LIKE1 promoter and transcript analysis of hormone‐treated Arabidopsis seedlings revealed that AtD27LIKE1 is expressed in different tissues and affects ABA and auxin. Taken together, our work reports a cis / cis‐ β‐carotene isomerase that affects the content of both cis ‐carotenoid‐derived plant hormones, ABA and SLs.
Publisher: Cold Spring Harbor Laboratory
Date: 07-06-2022
DOI: 10.1101/2022.06.07.495147
Abstract: The enzyme DWARF27 (D27) catalyzes the reversible isomerization of all- trans - into 9- cis -β-carotene, initiating strigolactone (SL) biosynthesis. Genomes of higher plants encode two D27-homologs, D27-like1 and -like2, with unknown functions. Here, we investigated the enzymatic activity and biological function of the Arabidopsis D27-like1. In vitro enzymatic assays and Expression in Synechocystis sp. PCC6803 revealed a yet not reported 13- cis /15- cis /9- cis - and a 9- cis /all- trans -β-carotene isomerization. Although disruption of AtD27-like1 did not cause SL deficiency phenotypes, overexpression of AtD27-like1 in the Atd27 mutant restored the more-branching phenotype, indicating a contribution of AtD27-like1 to SL biosynthesis. Accordingly, generated Atd27 Atd27like1 double mutants showed more pronounced branching phenotype, compared to Atd27. The contribution of AtD27-like1 to SL biosynthesis is likely due to its formation of 9- cis -β-carotene that was present at higher levels in AtD27-like1 overexpressing lines. In contrast, AtD27-like1 expression correlated negatively with the content of 9- cis -violaxanthin, a precursor of abscisic acid (ABA), in shoots. Consistently, ABA levels were higher in shoots and also in dry seeds of the Atd27like1 and Atd27 Atd27like1 mutants. Transgenic lines expressing β-glucuronidase (GUS) driven by the AtD27LIKE1 promoter and transcript analysis performed with hormone-treated Arabidopsis seedlings unraveled that AtD27LIKE1 is expressed in different tissues and regulated ABA and auxin. Taken together, our work revealed a cis / cis- β-carotene isomerase activity that affects the content of both cis -carotenoid derived plant hormones ABA and SLs.
Location: Saudi Arabia
Location: Saudi Arabia
No related grants have been discovered for Muhammad Jamil.