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Nitric Oxide Is Associated With Heterosis of Salinity Tolerance in Brassica napus L.

ABSTRACT: Heterosis is most frequently manifested as the superior performance of a hybrid than either of the parents, especially under stress conditions. Nitric oxide (NO) is a well-known gaseous signaling molecule that acts as a functional component during plant growth, development, and defense responses. In this study, the Brassica napus L. hybrid (F1, NJ4375 × MB1942) showed significant heterosis under salt stress, during both germination and post-germination periods. These phenotypes in the hybrid were in parallel with the better performance in redox homeostasis, including alleviation of reactive oxygen species accumulation and lipid peroxidation, and ion homeostasis, evaluated as a lower Na/K ratio in the leaves than parental lines. Meanwhile, stimulation of endogenous NO was more pronounced in hybrid plants, compared with parental lines, which might be mediated by nitrate reductase. Proteomic and biochemical analyses further revealed that protein abundance related to several metabolic processes, including chlorophyll biosynthesis, proline metabolism, and tricarboxylic acid cycle metabolism pathway, was greatly suppressed by salt stress in the two parental lines than in the hybrid. The above responses in hybrid plants were intensified by a NO-releasing compound, but abolished by a NO scavenger, both of which were matched with the changes in chlorophyll and proline contents. It was deduced that the above metabolic processes might play important roles in heterosis upon salt stress. Taken together, we proposed that heterosis derived from F1 hybridization in salt stress tolerance might be mediated by NO-dependent activation of defense responses and metabolic processes.

SUBMITTER: Zhang Y

PROVIDER: S-EPMC8194068 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background and aimsDrought reduces plant productivity, especially in the susceptible species Brassica napus. Water stress, mimicked by applications of 10 % polyethylene glycol (PEG), elevates nitric oxide (NO) in root cells after a few hours, contributing to degradation of the root apical meristems (RAMs), the function of which relies on auxin and brassinosteroids (BRs). Phytoglobins (Pgbs) are effective NO scavengers induced by this stress. This study examines the effects of BnPgb1 dysregulation in dehydrating B. napus roots, and the spatiotemporal relationship between Pgb1 and activities of auxin and BRs in the regulation of the RAM.MethodsBrassica napus lines over-expressing [BnPgb1(S)] or down-regulating [BnPgb1(RNAi)] BnPgb1 were exposed to PEG-induced water stress. The localization of BnPgb1, NO, auxin and PIN1 were analysed during the first 48 h, while the expression level of biosynthetic auxin and BR genes was measured during the first 24 h. Pharmacological treatments were conducted to assess the requirement of auxin and BR in dehydrating roots.Key resultsDuring PEG stress, BnPgb1 protein accumulated preferentially in the peripheral domains of the root elongation zone, exposing the meristem to NO, which inhibits polar auxin transport (PAT), probably by interfering with PIN1 localization and the synthesis of auxin. Diminished auxin at the root tip depressed the synthesis of BR and caused the degradation of the RAMs. The strength of BnPgb1 signal in the elongation zone was increased in BnPgb1(S) roots, where NO was confined to the most apical cells. Consequently, PAT and auxin synthesis were retained, and the definition of RAMs was maintained. Auxin preservation of the RAM required BRs, although BRs alone was not sufficient to fully rescue drought-damaged RAMs in auxin-depleted environments.ConclusionsThe tissue-specific localization of BnPgb1 and NO determine B. napus root responses to water stress. A model is proposed in which auxin and BRs act as downstream components of BnPgb1 signalling in the preservation of RAMs in dehydrating roots.

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Nitric Oxide Is Associated With Heterosis of Salinity Tolerance in Brassica napus L.

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