Comparison of Effect of Brassinosteroid and Gibberellin Biosynthesis Inhibitors on Growth of Rice Seedlings

Brassinosteroid（BR） and gibberellin（GA） are two predominant plant hormones that regulate plant cell elongation. Mutants disrupt the biosynthesis of these hormones and display different degrees of dwarf phenotypes in rice. Although the role of each plant hormone in promoting the longitudinal growth of plants has been extensively studied using genetic methods, their relationship is still poorly understood. In this study, we used two specific inhibitors targeting BR and GA biosynthesis to investigate the roles of BR and GA in growth of rice seedlings. Yucaizol, a specific inhibitor of BR biosynthesis, and Trinexapac-ethyl, a commercially available inhibitor of GA biosynthesis, were used. The effect of Yucaizol on rice seedlings indicated that Yucaizol significantly retarded stem elongation. The IC_（50） value was found to be approximately 0.8 μmol/L. Yucaizol also induced small leaf angle phenocopy in rice seedlings, similarly to BR-deficient rice, while Trinexapac-ethyl did not. When Yucaizol combined with Trinexapac-ethyl was applied to the rice plants, the mixture of these two inhibitors retarded stem elongation of rice at lower doses. Our results suggest that the use of a BR biosynthesis inhibitor combined with a GA biosynthesis inhibitor may be useful in the development of new technologies for controlling rice plant height.

In-Vitro Micropropagation and Acclimatization of an Endangered Native Orchid Using Organic Supplements

In-vitro propagation is a technique that provides a vital solution for the conservation of endangered orchid species. The media used in tissue culture can be modified through the addition of inexpensive organic materials as an alternative to expensive synthetic additives. Some organic sources, such as coconut water and fruit juice, contain significant amounts of vitamins, amino acids, and organic compounds which can act as growth regulators, making these organic sources excellent additives for in-vitro cultivation. The aim of this study was to develop a protocol for in-vitro micropropagation and acclimatization of Epidendrum nocturnum using organic supplements in the growth media and various substrates at the acclimatization stage. Banana powder, coconut water, and potato dextrose were added to a basal seed sowing media and evaluated for seed germination percentage and plantlet growth. In addition, various substrates such as coconut coir, horticultural charcoal, sphagnum moss, and wood bark were evaluated for height, number of leaves, and number of shoots in the acclimatization portion of this study. The culture medium with coconut water showed a greater germination percentage (71.00% and 76.75%) compared with the control (37.50% and 45.50%) at 60 and 90 days after seed sowing, respectively. Media with organic supplements showed greater values of plant length and number of roots compared with the control. The combination of coconut coir and horticultural charcoal was shown to be more efficient than the combination of sphagnum moss, horticultural charcoal, and wood bark, as results showed greater values of plant height and number of leaves at 30, 90, and 120 days after transplantation in acclimatization of E. nocturnum.

Effects of the nitrification inhibitor nitrapyrin and the plant growth regulator gibberellic acid on yield-scale nitrous oxide emission in maize fields under hot climatic conditions

Nitrification inhibitors are widely used in agriculture to mitigate nitrous oxide(N_(2)O)emission and increase crop yield.However,no concrete information on their mitigation of N_(2)O emission is available under soil and environmental conditions as in Pakistan.A field experiment was established using a silt clay loam soil from Peshawar,Pakistan,to study the effect of urea applied in combination with a nitrification inhibitor,nitrapyrin(2-chloro-6-tri-chloromethyl pyridine),and/or a plant growth regulator,gibberellic acid(GA_3),on N_(2)O emission and the nitrogen(N)uptake efficiency of maize.The experimental design was a randomized complete block with five treatments in four replicates:control with no N(CK),urea(200 kg N ha^(-1))alone,urea in combination with nitrapyrin(700 g ha^(-1)),urea in combination with GA_3(60 g ha^(-1)),and urea in combination with nitrapyrin and GA_3.The N_(2)O emission,yield,N response efficiency,and total N uptake were measured during the experimental period.The treatment with urea and nitrapyrin reduced total N_(2)O emission by 39%–43%and decreased yield-scaled N_(2)O emission by 47%–52%,relative to the treatment with urea alone.The maize plant biomass,grain yield,and total N uptake increased significantly by 23%,17%,and 15%,respectively,in the treatment with urea and nitrapyrin,relative to the treatment with urea alone,which was possibly due to N saving,lower N loss,and increased N uptake in the form of ammonium;they were further enhanced in the treatment with urea,nitrapyrin,and GA_3 by 27%,36%,and 25%,respectively,probably because of the stimulating effect of GA_3 on plant growth and development and the reduction in biotic and abiotic stresses.These results suggest that applying urea in combination with nitrapyrin and GA_3 has the potential to mitigate N_(2)O emission,improve N response efficiency,and increase maize yield.

In Vitro Micropropagation of Himalayan Weeping Bamboo, Drepanostachyum falcatum

Plant growth hormone BAP (benzyl amino purine), KIN (kinetin), NAA (1-naphthalene acetic acid) and IBA (indole-3 butyric acid) effect was studied on in vitro multiplication of shoots and rooting of Drepanostachyum falcatum. In vitro micropropagation of himalayan weeping bamboo is explained by in vitro shoot induction and proliferation. Excised explant with axillary bud is surface sterilized with 0.1% HgCl2 for 10 - 12 minutes, cleaned with 90% ethanol and inoculated on liquid Murashige and Skoog (MS) culture medium supplemented with different concentrations of BAP/ KIN. Effect of BAP/KIN on shoot induction is with different rate and number of shoots produced by explants with axillary bud cultured on MS media supplemented with 0.0 mg/L BAP/KIN - 5.5 mg/L BAP/KIN. Shoot multiplication with highest rate is achieved on MS medium supplemented with 3.5 mg/L BAP after 4th sub-culturing. The most effective with highest rate and number of root induction combination is 6.5 mg/L IBA after 5 weeks. The roots produced by 6.5 mg/L IBA is best compared with other combination of auxin NAA (1-naphthalene acetic acid).

Establishment of a selectable marker recycling system for iterative gene editing in Fusarium fujikuroi

Gibberellic acid(GA3)is a vital plant growth hormone widely used in agriculture.Currently,GA3 production relies on liquid fermentation by the filamentous fungus Fusarium fujikuroi.However,the lack of an effective selection marker recycling system hampers the application of metabolic engineering technology in F.fujikuroi,as multiple-gene editing and positive-strain screening still rely on a limited number of antibiotics.In this study,we developed a strategy using pyr4-blaster and CRISPR/Cas9 tools for recycling orotidine-5'-phosphate decarboxylase(Pyr4)selection markers.We demonstrated the effectiveness of this method for iterative gene integration and large gene-cluster deletion.We also successfully improved GA3 titers by overexpressing geranylgeranyl pyrophosphate synthase and truncated 3-hydroxy-3-methyl glutaryl coenzyme A reductase,which rewired the GA3 biosynthesis pathway.These results highlight the efficiency of our established system in recycling selection markers during iterative gene editing events.Moreover,the selection marker recycling system lays the foundation for further research on metabolic engineering for GA3 industrial production.