Cross-talk between nitric oxide and Ca (2+) in elevated CO 2-induced lateral root formation

Insights into the environmental factors shaping lateral root development

Roots are important organs of plants. Plants rely on roots for water, nutrients, and organic salts. In the whole root system, lateral roots (LRs) account for a large proportion and are critical to the development of the plant. Many environmental factors affect LR development. Therefore, a systematic understanding of these factors can provide a theoretical basis for creating optimal growth conditions for plants. In this paper, the factors affecting LR development are systematically and comprehensively summarized, and the molecular mechanism and regulatory network of LR development are described. Changes in the external environment not only lead to hormone homeostasis in plants but also affect the composition and activity of rhizosphere microbial communities, which in turn affect plants' nitrogen and phosphorus uptake and growth dynamics. LR development is influenced by hormone levels and external environment. In particular, auxin and abscisic acid coordinate with each other to maintain normal LR development. Of course, changes in the external environment are also important for root development, and they affect the intrinsic hormone levels of plants by affecting the accumulation and transport of hormones. For example, nitrogen, phosphorus, reactive oxygen species, nitric oxide, water, drought, light, and rhizosphere microorganisms affect LR development and plant tolerance in a variety of ways, including regulating hormone levels. This review summarizes the factors affecting LR development and the regulatory network and points out the direction for future research.

Nitric oxide: A core signaling molecule under elevated GHGs (CO2, CH4, N2O, O3)-mediated abiotic stress in plants

Nitric oxide (NO), an ancient molecule with multiple roles in plants, has gained momentum and continues to govern plant biosciences-related research. NO, known to be involved in diverse physiological and biological processes, is a central molecule mediating cellular redox homeostasis under abiotic and biotic stresses. NO signaling interacts with various signaling networks to govern the adaptive response mechanism towards stress tolerance. Although diverging views question the role of plants in the current greenhouse gases (GHGs) budget, it is widely accepted that plants contribute, in one way or another, to the release of GHGs (carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and ozone (O3)) to the atmosphere, with CH4 and N2O being the most abundant, and occur simultaneously. Studies support that elevated concentrations of GHGs trigger similar signaling pathways to that observed in commonly studied abiotic stresses. In the process, NO plays a forefront role, in which the nitrogen metabolism is tightly related. Regardless of their beneficial roles in plants at a certain level of accumulation, high concentrations of CO2, CH4, and N2O-mediating stress in plants exacerbate the production of reactive oxygen (ROS) and nitrogen (RNS) species. This review assesses and discusses the current knowledge of NO signaling and its interaction with other signaling pathways, here focusing on the reported calcium (Ca2+) and hormonal signaling, under elevated GHGs along with the associated mechanisms underlying GHGs-induced stress in plants.

Cinnamaldehyde promotes root branching by regulating endogenous hydrogen sulfide

BACKGROUND

Cinnamaldehyde (CA) has been widely applied in medicine and food preservation. However, whether and how CA regulates plant physiology is largely unknown. To address these gaps, the present study investigated the beneficial effect of CA on root branching and its possible biochemical mechanism.

RESULTS

The lateral root (LR) formation of pepper seedlings could be markedly induced by CA at specific concentrations without any inhibitory effect on primary root (PR) growth. CA could induce the generation of endogenous hydrogen sulfide (H2S) by increasing the activity of L-cysteine desulfhydrase in roots. By fluorescently tracking endogenous H2S in situ, it could be clearly observed that H2S accumulated in the outer layer cells of the PR where LRs emerge. Sodium hydrosulfide (H2S donor) treatment induced LR formation, while hypotaurine (H2S scavenger) showed an adverse effect. The addition of hypotaurine mitigated the CA-induced increase in endogenous H2S level, which in turn counteracted the inducible effect of CA on LR formation.

CONCLUSION

CA showed great potential in promoting LR formation, which was mediated by endogenous H2S. These results not only shed new light on the application of CA in agriculture but also extend the knowledge of H2S signaling in the regulation of root branching.

In site bioimaging of hydrogen sulfide uncovers its pivotal role in regulating nitric oxide-induced lateral root formation

Hydrogen sulfide (H₂S) is an important gasotransmitter in mammals. Despite physiological changes induced by exogenous H₂S donor NaHS to plants, whether and how H₂S works as a true cellular signal in plants need to be examined. A self-developed specific fluorescent probe (WSP-1) was applied to track endogenous H₂S in tomato (Solanum lycopersicum) roots in site. Bioimaging combined with pharmacological and biochemical approaches were used to investigate the cross-talk among H₂S, nitric oxide (NO), and Ca²⁺ in regulating lateral root formation. Endogenous H₂S accumulation was clearly associated with primordium initiation and lateral root emergence. NO donor SNP stimulated the generation of endogenous H₂S and the expression of the gene coding for the enzyme responsible for endogenous H₂S synthesis. Scavenging H₂S or inhibiting H₂S synthesis partially blocked SNP-induced lateral root formation and the expression of lateral root-related genes. The stimulatory effect of SNP on Ca²⁺ accumulation and CaM1 (calmodulin 1) expression could be abolished by inhibiting H₂S synthesis. Ca²⁺ chelator or Ca²⁺ channel blocker attenuated NaHS-induced lateral root formation. Our study confirmed the role of H₂S as a cellular signal in plants being a mediator between NO and Ca²⁺ in regulating lateral root formation.