Strigolactones Improve Plant Growth, Photosynthesis, and Alleviate Oxidative Stress under Salinity in Rapeseed (Brassica napus L.) by Regulating Gene Expression

Abstract

Rapeseed (Brassica napus L.) is a very important edible oil crop in the world, and the production is inhibited by abiotic stresses, such as salinity. Plant hormones can alleviate the stress by regulating the physiological processes and gene expression. To study the plant responses to salinity in combination with GR24, a synthesized strigolactone, the oilseed rape variety (Zhongshuang 11) replications were grown in the pots in a controlled growth chamber under three levels of salinity (0, 100, and 200 mM NaCl) and 0.18 μM GR24 treatments at the seedling stage for 7 days. The results showed that salinity depressed the shoots and roots growth, whereas GR24 improved the growth under salt stress. Leaf chlorophyll contents and gas exchange parameters (net photosynthetic rates, stomatal conductance, intercellular CO2 concentration, and transpiration rate) were also reduced significantly with increasing salinity, and these effects could be partially reversed by GR24 application. Additionally, GR24 treatment significantly increased and decreased the photosystem II quantum yield and non-photochemical quenching, respectively, under salinity stress conditions. The activities of peroxidase and superoxide dismutase increased, and lipid peroxidation measured by the level of malondialdehyde reduced due to GR24 application. The transcriptome analysis of root and shoot was conducted. Three hundred and forty-two common differentially expressed genes (DEGs) after GR24 treatment and 166 special DEGs after GR24 treatment under salinity stress were identified in root and shoot. The DEGs in root were significantly more than that in shoot. Quantitative PCR validated that the stress alleviation was mainly related to the gene expression of tryptophan metabolism, plant hormone signal transduction, and photosynthesis.

Strigolactones in plant adaptation to abiotic stresses: An emerging avenue of plant research

“…These findings collectively provided important clues regarding the potential of SLs in regulating plant responses and adaptation to environmental stresses. Thus, an increasing number of studies have recently focused on the implications of SLs in the adaptation of plants to environmental constraints and have reported many novel findings (Bu et al, ; Cooper et al, ; C. V. Ha et al, ; Liu et al, ; Lv et al, ; Ma et al, ; Ruiz‐Lozano et al, ; Umehara et al, ; Visentin et al, ; Y. Zhang, Lv, & Wang, ). Moreover, the connection of SLs in AM symbiosis‐mediated improvement of physiological responses has also been reported in plants under abiotic stresses, such as high salinity and drought (Aroca et al, ; Ruiz‐Lozano et al, ).…”

Comparing and Contrasting the Multiple Roles of Butenolide Plant Growth Regulators: Strigolactones and Karrikins in Plant Development and Adaptation to Abiotic Stresses

“…For instance, in the ABA-deficient mutants up14 (maize), notabilis and sitiens (tomato), the transcriptional levels of the SL synthesis genes CCD7 and CCD8 are reduced, which leads to decreased content of SLs in root secretion [141]. Further, SL synthesis is regulated by ABA in Arabidopsis [41]. KARs negatively regulate seed germination by inhibiting GA synthesis and promoting ABA synthesis in soybean [100].…”

“…In recent years, substantial evidence has demonstrated that SLs and KARs are involved in the regulation of the plant responses to abiotic stress [8,37,38,[41][42][43]46,63,143,190,191] (Table 1). SL levels are finely modulated under various types of abiotic stress.…”

“…Interestingly, drought increases the abundance of transcripts of the SL-biosynthetic genes SlCCD7 and SlCCD8 in tomato shoots and the D27 and MAX1 homologs Os01g0700900, Os01g0701400, Os02g0221900, and Os06g0565100 in rice shoots [38,40]. Additionally, the SL-biosynthetic genes MAX3 and MAX4 are significantly induced by dehydration and salinity in leaves of Arabidopsis [41]. Essentially, these findings suggest that an efficient activation of SL biosynthesis is triggered in response to osmotic stress, leading to the activation of SL signaling, which positively regulates the tolerance of these adverse conditions.…”

“…SLs also promote beneficial symbiotic relationships between host plants and mycorrhizal fungi [35,36]. The biosynthesis and signaling of SLs are regulated by various abiotic stress factors [37][38][39][40], including the recently reported SL involvement in responding to nutrient deprivation, drought, chilling and salinity [38,[40][41][42][43][44][45][46][47][48][49][50]. Such studies provide new insights into the novel roles SL signaling plays in the regulation of plant adaptation to adverse environmental conditions [51][52][53][54].Karrikins (KARs) are found in smoke released from the heating or combustion of plant material, after which they can stimulate the germination of dormant seeds [55][56][57][58].…”