Role of ethylene in abnormal shoot growth induced by high concentration of brassinolide in rice seedlings

Abstract

A high concentration of brassinolide (BL) induced abnormal shoot shape in rice seedlings, that is, the newly developed leaf sheath was shorter than the old sheath, and increased the number of leaves. The involvement of ethylene and cyanide, co-metabolites during ethylene biosynthesis, in abnormal shoot growth was analyzed by comparing the action mechanism of BL with that of quinclorac in barnyard grass seedlings. BL strongly stimulated ethylene production, and the amount of ethylene and the third leaf sheath length in rice seedlings were negatively correlated. Exogenously applied ethephon also induced abnormal growth of rice seedlings. L-a -aminoethoxyvinyl-glycine (AVG), an ethylene biosynthetic inhibitor, partially reversed abnormal shoot growth. The level of endogenous cyanide was low in rice seedlings, because of the high level of b-cyanoalanine synthase (CAS) activity, and exogenously applied KCN did not induce abnormal shoot growth. The results indicate that BL-induced abnormal shoot growth of rice seedlings was probably mediated by ethylene production.

Quinclorac resistance in Echinochloa phyllopogon is associated with reduced ethylene synthesis rather than enhanced cyanide detoxification by β‐cyanoalanine synthase

“…Arabidopsis and rice were grown on solid MS media for 2 weeks as described above and used in the enzyme assay. β‐CAS activity was determined following the previous procedures with certain modifications. Shoots (500 mg) were homogenized in liquid nitrogen in a mortar and pestle, extracted with 2.5 mL of ice‐cold 0.1 M Tris–HCl buffer (pH 8.5), and sonicated by ultrasonic homogenizer on ice for 30 s. The suspension was centrifuged at 10000 × g and 4 °C for 10 min.…”

Ethylene Biosynthesis Inhibition Combined with Cyanide Degradation Confer Resistance to Quinclorac in Echinochloa crus-galli var. mitis

“…Plant samples were collected 0, 12, and 24 h after adding quinclorac. The β-CAS activity was determined by the previously described procedure [63]. Then, 0.1 M Tris-HCl buffer (pH 8.5) was used to extract the powdered shoots.…”

An Insight of Quinclorac Resistance Mechanism in Early Watergrass ( Echinochloa oryzoides )

“…Enzyme extract was incubated for 30 min at 35 °C after extracting with 0.1 M Tris-HCl buffer. Absorbance was recorded at 650 nm using Na 2 S as standard (Chon et al, 2008).…”