Alleviating dormancy in Brassica oleracea seeds using NO and KAR1 with ethylene biosynthetic pathway, ROS and antioxidant enzymes modifications

Abstract

BackgroundSeed dormancy is a prevailing condition in which seeds are unable to germinate, even under favorable environmental conditions. Harvested Brassica oleracea (Chinese cabbage) seeds are dormant and normally germinate (poorly) at 21 °C. This study investigated the connections between ethylene, nitric oxide (NO), and karrikin 1 (KAR1) in the dormancy release of secondary dormant Brassica oleracea seeds.ResultsNO and KAR1 were found to induce seed germination, and stimulated the production of ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC), and both ethylene biosynthesis enzyme ACC oxidase (ACO) [1] and ACC synthase (ACS) [2]. In the presence of NO and KAR1, ACS and ACO activity reached maximum levels after 36 and 48 h, respectively. The inhibitor of ethylene 2,5-norbornadiene (NBD) had an adverse effect on Brassica oleracea seed germination (inhibiting nearly 50% of germination) in the presence of NO and KAR1. The benefits from NO and KAR1 in the germination of secondary dormant Brassica oleracea seeds were also associated with a marked increase in reactive oxygen species (ROS) (H2O2 and O2˙ˉ) and antioxidant enzyme activity at early germination stages. Catalase (CAT) and glutathione reductase (GR) activity increased 2 d and 4 d, respectively, after treatment, while no significant changes were observed in superoxide dismutase (SOD) activity under NO and KAR1 applications. An increase in H2O2 and O2˙ˉ levels were observed during the entire incubation period, which increasing ethylene production in the presence of NO and KAR1. Abscisic acid (ABA) contents decreased and glutathione reductase (GA) contents increased in the presence of NO and KAR1. Gene expression studies were carried out with seven ethylene biosynthesis ACC synthases (ACS) genes, two ethylene receptors (ETR) genes and one ACO gene. Our results provide more evidence for the involvement of ethylene in inducing seed germination in the presence of NO and KAR1. Three out of seven ethylene biosynthesis genes (BOACS7, BOACS9 and BOACS11), two ethylene receptors (BOETR1 and BOETR2) and one ACO gene (BOACO1) were up-regulated in the presence of NO and KAR1.ConclusionConsequently, ACS activity, ACO activity and the expression of different ethylene related genes increased, modified the ROS level, antioxidant enzyme activity, and ethylene biosynthesis pathway and successfully removed (nearly 98%) of the seed dormancy of secondary dormant Brassica olereace seeds after 7 days of NO and KAR1 application.

KAI2 regulates seedling development by mediating light-induced remodelling of auxin transport

“…It has long been speculated that KAI2 targets the SMAX1 (SUPPRESSOR OF MAX2 LIKE 1) and SMXL2 proteins for degradation, analogous to the D14-SMXL7/D53 interaction 2 , and recent data provide confirmation of this idea 8,22 . However, apart from an increase in ethylene biosynthesis in the root 23,24 , KAI2-mediated signalling events downstream of SMAX1/SMXL2 remain unclear. There are some well-established genes upregulated in response to KAI2 signalling, including its homologue DWARF14-LIKE2 ( DLK2 ) and KAI2-UPREGULATED F-BOX1 ( KUF1 ) 1 , but the function of these genes remains enigmatic, and DLK2 has no obvious role in development 25 .…”

The karrikin signaling regulator SMAX1 controls Lotus japonicus root and root hair development by suppressing ethylene biosynthesis

“…Given the evidence presented here, this sole dependence on ACS7 (and possibly ACS7-like) is likely conserved in L. japonicus. Ethylene signaling downstream of KAR signaling may play a role also in seed germination since an increase in ACS activity and ethylene release from germinating Brassica oleracea seeds upon exogenous KAR 1 treatment was recently reported (51).…”

Assessment of the Germination Potential of Brassica oleracea Seeds Treated with Karrikin 1 and Cyanide, Which Modify the Ethylene Biosynthetic Pathway

“…The seed water content was measured according to the protocol of Sami et al (2019). First, the fresh weight of the samples was recorded.…”

“…Although KAR2 to KAR6 were also found to regulate seed germination in different plant species, their efficiency was not greater than that of KAR1 (Flematti et al2009). Furthermore, KAR1 successfully increased the seedling vigor of several commercial plant species (Flematti et al 2010;Sami et al 2019). The possible mechanism of action by which KAR1 stimulates seed germination is still not well understood.…”