Regulatory mechanism of abscisic acid signaling

The ZmbHLH47-ZmSnRK2.9 Module Promotes Drought Tolerance in Maize

Drought stress globally poses a significant threat to maize (Zea mays L.) productivity and the underlying molecular mechanisms of drought tolerance remain elusive. In this study, we characterized ZmbHLH47, a basic helix-loop-helix (bHLH) transcription factor, as a positive regulator of drought tolerance in maize. ZmbHLH47 expression was notably induced by both drought stress and abscisic acid (ABA). Transgenic plants overexpressing ZmbHLH47 displayed elevated drought tolerance and ABA responsiveness, while the zmbhlh47 mutant exhibited increased drought sensitivity and reduced ABA sensitivity. Mechanistically, it was revealed that ZmbHLH47 could directly bind to the promoter of ZmSnRK2.9 gene, a member of the subgroup III SnRK2 kinases, activating its expression. Furthermore, ZmSnRK2.9-overexpressing plants exhibited enhanced ABA sensitivity and drought tolerance, whereas the zmsnrk2.9 mutant displayed a decreased sensitivity to both. Notably, overexpressing ZmbHLH47 in the zmsnrk2.9 mutant closely resembled the zmsnrk2.9 mutant, indicating the importance of the ZmbHLH47-ZmSnRK2.9 module in ABA response and drought tolerance. These findings provided valuable insights and a potential genetic resource for enhancing the environmental adaptability of maize.

A briefly overview of the research progress for the abscisic acid analogues

Abscisic acid (ABA) is an important plant endogenous hormone that participates in the regulation of various physiological processes in plants, including the occurrence and development of somatic embryos, seeddevelopment and dormancy. ABA is called “plant stress resistance factor”, while with the limitation of the rapid metabolic inactivation and photoisomerization inactivation of ABA for its large-scale use. Understanding the function and role of ABA in plants is of great significance to promote its application. For decades, scientists have conducted in-depth research on its mechanism of action and signaling pathways, a series of progress were achieved, and hundreds of ABA analogues (similar in structure or function) have been synthesized to develop highly active plant growth regulators and tools to elucidate ABA perception. In this review, we summarize a variety of ABA analogues, especially the ABA receptor analogues, and explore the mechanisms of ABA action and catabolism, which will facilitate the development of novel ABA analogues with high biological activities.

Tetrahydroquinolinyl phosphinamidates and phosphonamidates enhancing tolerance towards drought stress in crops via interaction with ABA receptor proteins

New phosphorous-containing lead structures against drought stress in crops interacting with RCAR/(PYR/PYL) receptor proteins were identified starting from in-depth SAR studies of related sulfonamide lead structures and protein docking studies. A converging 6-step synthesis via phosphinic chlorides and phosphono chloridates as key intermediates afforded envisaged tetrahydroquinolinyl phosphinamidates and phosphonamidates. Whilst tetrahydroquinolinyl phosphonamidates 13a,b exhibited low to moderate target affinities, the corresponding tetrahydroquinolinyl phosphinamidates 12a,b revealed confirmed strong affinities for RCAR/ (PYR/PYL) receptor proteins in Arabidopsis thaliana on the same level as essential plant hormone abscisic acid (ABA) combined with promising efficacy against drought stress in vivo (broad-acre crops wheat and canola).

Identifying new lead structures to enhance tolerance towards drought stress via high-throughput screening giving crops a quantum of solace

Novel synthetic lead structures interacting with RCAR/(PYR/PYL) receptor proteins were identified based on the results of a high-throughput screening campaign of a large compound library followed by focused SAR studies of the three most promising hit clusters. Whilst indolinylmethyl sulfonamides 8y,z and phenylsulfonyl ethylenediamines 9y,z showed strong affinities for RCAR/ (PYR/PYL) receptor proteins in wheat, thiotriazolyl acetamides 7f,s exhibited promising efficacy against drought stress in vivo (wheat, corn and canola) combined with confirmed target interaction in wheat and arabidopsis thaliana. Remarkably, binding affinities of several representatives of 8 and 9 were on the same level or even better than the essential plant hormone abscisic acid (ABA).

The Maize Clade A PP2C Phosphatases Play Critical Roles in Multiple Abiotic Stress Responses

As the core components of abscisic acid (ABA) signal pathway, Clade A PP2C (PP2C-A) phosphatases in ABA-dependent stress responses have been well studied in Arabidopsis. However, the roles and natural variations of maize PP2C-A in stress responses remain largely unknown. In this study, we investigated the expression patterns of ZmPP2C-As treated with multiple stresses and generated transgenic Arabidopsis plants overexpressing most of the ZmPP2C-A genes. The results showed that the expression of most ZmPP2C-As were dramatically induced by multiple stresses (drought, salt, and ABA), indicating that these genes may have important roles in response to these stresses. Compared with wild-type plants, ZmPP2C-A1, ZmPP2C-A2, and ZmPP2C-A6 overexpression plants had higher germination rates after ABA and NaCl treatments. ZmPP2C-A2 and ZmPP2C-A6 negatively regulated drought responses as the plants overexpressing these genes had lower survival rates, higher leaf water loss rates, and lower proline accumulation compared to wild type plants. The natural variations of ZmPP2C-As associated with drought tolerance were also analyzed and favorable alleles were detected. We widely studied the roles of ZmPP2C-A genes in stress responses and the natural variations detected in these genes have the potential to be used as molecular markers in genetic improvement of maize drought tolerance.