Abscisic acid and ethephon regulation of cellulase in the endosperm cap and radicle during lettuce seed germination

Abstract

The purpose of this study was to investigate the role of cellulase in endosperm cap weakening and radicle elongation during lettuce (Lactuca sativa L.) seed germination. The application of abscisic acid (ABA) or ethephon inhibits or promotes germination, respectively, by affecting endosperm cap weakening and radicle elongation. Cellulase activities, and related protein and transcript abundances of two lettuce cellulase genes, LsCEL1 and LsCEL2, increase in the endosperm cap and radicle prior to radicle protrusion following imbibition in water. ABA or ethephon reduce or elevate, respectively, cellulase activity, and related protein and transcript abundances in the endosperm cap. Taken together, these observations suggest that cellulase plays a role in endosperm cap weakening and radicle elongation during lettuce seed germination, and that the regulation of cellulase in the endosperm cap by ABA and ethephon play a role in endosperm cap weakening. However, the influence of ABA and ethephon on radicle elongation may not be through their effects on cellulase.Keywords: Abscisic acid; cellulase; ethephon; endosperm cap weakening; lettuce seed germination Citation: Chen B, Ma J, Xu Z, Wang X (2016) Abscisic acid and ethephon regulation of cellulase in the endosperm cap and radicle during lettuce seed germination.

Involvement of Polyamine Oxidase-Produced Hydrogen Peroxide during Coleorhiza-Limited Germination of Rice Seeds

“…We used NBT and DAB, respectively, to stain seeds for O 2 - and H 2 O 2 as described ( Zhang et al, 2014 ; Chen et al, 2016 ). After rice seeds had imbibed water or 5 mM guazatine for 3, 6, 12, 24, or 48 h, five whole seeds and five half granule seeds containing the embryos were removed and incubated with 1 mM NBT in 10 mM Tris-HCl (pH 7.0), or 1 mg/mL DAB (pH 3.8) at room temperature for 30 min, then washed with double-distilled water, and photographed using the stereomicroscope (SteREO Lumar V12, Zeiss, Germany).…”

“…The rate of O 2 - production (nmol O 2 - ⋅min -1 ⋅g -1 FW) and H 2 O 2 concentration (μmol⋅g -1 FW) were spectro photometrically measured as described [fresh weight (FW); Zhang et al, 2014 ; Chen et al, 2016 ]. Thirty embryos at each aforementioned imbibition time points were used for each type of measurement, and the mean value ± SE of three biological replicates were calculated.…”

“…POD activity was detected histochemically by TMB staining as described ( Zhang et al, 2014 ; Chen et al, 2016 ). Rice seeds were imbibed in water or 5 mM guazatine for the aforementioned five times.…”

“…In monocot seeds, particularly those of cereals, e.g., barley ( Hordeum vulgare ), rice ( Oryza sativa ), and purple false brome ( Brachypodium distachyon ), the coleorhiza, which is a non-vascularized multicellular embryonic tissue covering the seminal seed root, is believed to regulate emergence of the radicle during germination ( Millar et al, 2006 ; Gonzalez-Calle et al, 2015 ). It has been assumed that dicot seed germination is controlled by the mechanical force of the imbibed, elongating radicle on the endosperm cap and by inherent cap weakening driven by enzymatic (i.e., endo-β-1,4-mannanases and pectin methylesterases) and non-enzymatic reactions [e.g., those involving reactive oxygen species (ROS); Nonogaki et al, 2010 ; Zhang et al, 2014 ; Scheler et al, 2015 ; Chen et al, 2016 ]. Given the physical and chemical similarities of dicot and monocot seed structures, logically similar enzymatic and non-enzymatic mechanisms would be required during monocot seed germination.…”

Enzyme activity in the micropylar region of Melanoxylon brauna Schott seeds during germination under heat stress conditions

“…β-Glucosidases break the chemical bond between the glucose units of cellobiose, releasing free glucose. By doing so, they contribute to the weakening of the micropylar endosperm and provide energy for radicle emergence, as observed in seeds of Coffea arabica (Castro and Pereira, 2010), Lactuca sativa (Chen et al, 2016) and L. sativum (Ogórek, 2016). Enzyme activity was related to germination percentage, but was less affected by high temperatures.…”