Programmed cell death, antioxidant response and oxidative stress in wheat flag leaves induced by chemical hybridization agent SQ-1

Abstract

Male sterility induced by a chemical hybridization agent (CHA) is an important tool for utilizing crop heterosis. Leaves, especially the flag leaves, as CHA initial recipients play a decisive role in inducing male sterility. To investigate effects of different treatment times of CHA-SQ-1 used, morphological, biochemical and physiological responses of wheat flag leaves were detected in this study. CHA induced programmed cell death (PCD) as shown in terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL) and DNA laddering analysis. In the early phase, CHA-SQ-1 triggered organelle changes and PCD in wheat leaves accompanied by excess production of reactive oxygen species (O 2-. and H 2 O 2) and down-regulation of the activity of superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (POD). Meanwhile, leaf cell DNAs showed ladder-like patterns on agarose gel, indicating that CHA-SQ-1 led to the activation of the responsible endonuclease. The oxidative stress assays showed that lipid peroxidation was strongly activated and photosynthesis was obviously inhibited in SQ-1-induced leaves. However, CHA contents in wheat leaves gradually reduced along with the time CHA-SQ-1 applied. Young flags returned to an oxidative/antioxidative balance and ultimately developed into mature green leaves. These results provide explanation of the relations between PCD and anther abortion and practical application of CHA for hybrid breeding.

Cyclin-Dependent Kinase Inhibitor Gene TaICK1 acts as a Potential Contributor to Wheat Male Sterility induced by a Chemical Hybridizing Agent

“…CHA SQ-1 can effectively induce male sterility in most wheat varieties, reaching rates of up to 95%. Meanwhile, the seed setting rate of artificial saturation pollination can reach 98% [15]. This result shows the great potential of utilizing heterosis.…”

“…These results demonstrate that SQ-1 has tremendous application potential in wheat hybrid seed production. However, the degree of male sterility induced by SQ-1 in some fine varieties is unsatisfactory for hybrid seed production [15,16]. As a result, some fine varieties cannot be used as parents in hybrid seed production.…”

Mitochondrial Dysfunction Causes Oxidative Stress and Tapetal Apoptosis in Chemical Hybridization Reagent-Induced Male Sterility in Wheat

“…Details of the wheat treatment were as previously described ( Liu et al, 2014 ; Wang et al, 2015a ). Wheat cultivar “Xinong 1376” was treated by SQ-1 at a rate of 5.0 kg/ha, and sprayed when the crop was around the 8.5 stage based on the Feekes’ scale ( Large, 1954 ; Wang et al, 2016 ). All plants were conventionally grown in a wheat field of the experimental station of the Northwest Agriculture and Forestry University in Yangling, China.…”

“…Anthers at five stages (tetrad stage, early uninucleate stage, later-uninucleate stage, binucleate stage and trinucleate stage) were also collected. Anther soluble sugar levels were measured using anthrone colorimetry method as described by Oliver et al (2005) , and starch content was measured according to Dorion et al (1996) and Wang et al (2016) .…”

“…Recently, more than applicable 40 CHAs have been reported ( Singh et al, 2015b ), some of which are found effective in inducing pollen sterility, such as RH007 ( Mizelle et al, 1989 ), SC2053 ( Fan et al, 1998 ), and Genesis ( Singh et al, 2010 ). Compared with them, SQ-1 is an ideal chemical hybridization agent which could induce male sterility by changing the cell microstructure ( Wang et al, 2016 ), triggering programmed cell death (PCD) ( Wang et al, 2015a , 2016 ), striking the oxidative/antioxidative balance ( Wang et al, 2016 ) and increasing the cell membrane permeability ( Song et al, 2015 ). Despite some progress toward understanding the mechanisms of male sterility has been made, such as reactive oxygen and aliphatic metabolism ( Ba et al, 2013 , 2014a ), DNA methylation ( Ba et al, 2014b ), cell morphological ( Wang et al, 2015a ), transcriptome ( Zhu et al, 2015 ) and proteomics ( Song et al, 2015 ; Wang et al, 2015b ), the mechanisms underlying male sterility in plants resulting from CHA treatment remain elusive.…”