Investigating relative expression of AP1 homologous in different organs of black mustard (Brassica nigra L.): The effect of hydrogen sulfide (H2S) on flower stimulation and gene expression

Objective APETALA1 (AP1) gene plays an important role in promoting transition from vegetative to reproductive phase and determining the flower meristem identity. This research was conducted to investigate the AP1 relative expression in the black mustard plant (Brassica nigra L.). Also, the effect of hydrogen sulfide on flowering and its relative expression was investigated. Materials and methods Total RNA was extracted from the collected samples and used to make cDNA. Specific primers were designed and used for RT-PCR reaction based on the sequence alignment of AP1 homologous genes in plants of the same family. The relative expression of AP1 was studied in the reproductive phase in different organs such as root, stem, leaf, flower bud, sepal, petal, stamen and pistil. In addition, the effect of NaHS on flowering and relative gene expression in different developmental stages in vegetative shoots, generative shoots and flower buds was investigated. The intensity of expression was measured with ImageJ software and the data were compared with ANOVA statistical analysis and Duncan's test with a confidence factor of 95%. Results Studies of the relative expression of AP1 gene in different organs of the black mustard in the generative phase indicated that this gene is expressed in flower bud, sepal, petal and leaf, but no expression was observed in the root, stem, stamen and pistil. Also, its relative expression in samples treated with NaHS compared with the control group showed that the beginning of AP1 gene expression and consequently the transition to flowering is faster and earlier in plants treated with hydrogen sulfide. Thus, the treated plants had a shorter life cycle and flowered 8 days earlier. The comparison of its expression in vegetative shoots, reproductive shoots and flower buds did not show any significant difference in the same developmental stages, but expression higher levels was observed at the same sampling times in the treated samples compared with controls. No expression was observed in the control samples at the periods that the treated samples showed high expression and were in generative phase and flowering. Conclusions The relative expression of AP1 gene during developmental stages and its increase in the reproductive stage can confirm its role in the flowering process. NaHS induced flowering and in a 35-day life cycle, treated plants entered the reproductive phase 8 days earlier. Therefore, NaHS treatment, by shortening the vegetativ