New Abscisic Acid Derivatives Revealed Adequate Regulation of Stomatal, Transcriptional, and Developmental Responses to Conquer Drought

Abstract

The phytohormone abscisic acid (ABA) plays an important role in plant stress response, mainly against desiccation. Hence, ABA receptor agonists may function as agents to enhance drought tolerance in crops. ABA exhibits diverse functions that impact plant development and are regulated by various ABA receptor subfamilies. Indeed, we previously reported that 3′-alkyl ABAs exhibit diverse receptor specificities and that 3′-butyl ABA induced a drought stress response without eliciting growth inhibitory effects in Arabidopsis seedlings. Thus, to further investigate plant responses induced by 3′-butyl ABA, as well as the receptors that control the opposing stress and growth responses, we designed new 3′-alkyl ABA derivatives. In addition to the 3′-alkyl chain, a cyclopropyl group was attached to position 3 of ABA to occupy the C6 cleft in the ABA-binding pocket of the receptors, which served to increase the binding affinity and specificity to a certain receptor set. Additionally, the inhibitory activity of pyrabactin resistance 1 (PYR1) and PYR1-like (PYL1) proteins against type 2C protein phosphatase increased following incorporation of the 3-cyclopropyl group in all tested 3′-alkyl ABAs. Interestingly, 3′-butyl ABA induced the highest tolerance against drought stress, compared with 3-cyclopropyl derivatives. To investigate the molecular mechanism underlying the effects elicited by different chemical treatments, those of ABA derivatives on stomatal closure, growth, and gene expression were studied. Evaluation of the receptors activated by ABA derivatives and the plant responses revealed the induction of PYR1, PYL1, PYL2, and PYL5, mediated stomatal closure, and regulated transcription, consequently leading to drought tolerance in plants.

Responses of differentially expressed proteins and endogenous hormones in winter rapeseed (Brassica rapa L.) roots under water deficit stress

“…The water and minerals absorbed by the root system are also translocated to the aboveground parts from the roots and to vegetative organs of some plant species ( Solanum tuberosum L., Raphanus sativus L., etc.) (Blanco‐Touriñán et al, 2020b; Yoshida et al, 2021b). When plants experience water deficit, the roots are the first organs to produce stress signals, and thus, studies of the stress response of roots are highly important (Li, Li, et al, 2021c).…”

“…Stress‐related proteins are expressed to allow winter rapeseed roots to resist and adapt to water deficit. The related proteins also regulate root growth in winter rapeseed, and the root system architecture is regulated by endogenous hormones (Yoshida et al, 2021a). In conclusion, the response to water deficit stress is a complex process, and ROS, endogenous hormones and stress‐related proteins regulate the root system architecture and function, which together constitute the molecular mechanism underlying this response in winter rapeseed roots.…”

“…For the CK and MWD, 15 genes displayed the same up/downregulation patterns in both winter rapeseed varieties: Stress-related proteins are expressed to allow winter rapeseed roots to resist and adapt to water deficit. The related proteins also regulate root growth in winter rapeseed, and the root system architecture is regulated by endogenous hormones (Yoshida et al, 2021a). In conclusion, the response to water deficit stress is a complex process, and ROS, endogenous hormones and stress-related proteins regulate the T A B L E 2 Correlation analysis of the root system architecture, endogenous hormone contents and biochemical traits involving the cell membrane in winter rapeseed roots.…”

An efficient and scalable synthesis of a persistent abscisic acid analog (+)-tetralone ABA

“…ABA triggers plant responses to extremes of temperature and drought, and also plays numerous roles over a plant's life including growth, dormancy, primary and secondary metabolite production. 2–9…”

“…ABA triggers plant responses to extremes of temperature and drought, and also plays numerous roles over a plant's life including growth, dormancy, primary and secondary metabolite production. [2][3][4][5][6][7][8][9] The natural product (S)-ABA ( 1) is now produced on large scale by fermentation and is readily available. 10 (S)-ABA is commercially used for several applications including (i) enhancing the colour of red table grapes; (ii) as a seed treatment for hybrid seed production in corn; (iii) for increasing grain-filling rate and milling quality in rice; and (iv) as a fruit thinning agent for pears and apples.…”