Negotiating soil water deficit in mycorrhizal trifoliate orange plants: A gibberellin pathway

• Published in: Environmental and experimental botany 2024-03, Vol.219, p.105658, Article 105658
• Main Authors: Liu, Zhen, Cheng, Xiao-Fen, Zou, Ying-Ning, Srivastava, Anoop Kumar, Alqahtani, Mashael Daghash, Wu, Qiang-Sheng
• Format: Article
• Language: English
• Subjects: Citrus; DELLA; Drought; GA2ox; GA4; Mycorrhiza
• ISSN: 0098-8472; 1873-7307
• DOI: 10.1016/j.envexpbot.2024.105658

Gibberellins (GAs), an important endogenous hormone, serve a crucial regulatory role in plants’ resistance to environmental stress, whereas it is unclear whether and how arbuscular mycorrhizal fungi (AMF) regulate the profile of GAs in plants exposed to soil water deficit (SWD). This study aimed to analyze how Rhizoglomus intraradices inoculation affected plant growth performance, antioxidant enzyme activities, and the composition, synthesis, metabolism, and signaling pathways of GAs in the roots of trifoliate orange (Poncirus trifoliata) under a 10-week SWD. Although the SWD decreased both root AMF colonization and soil hyphal length, mycorrhizal plants nevertheless outperformed non-mycorrhizal plants in terms of growth performance, as well as peroxidase (70.0%) and catalase (149.2%) activities, indicating greater drought tolerance. A total of nine GAs compositions were detected in the roots, with bioactive GA4 exclusively found in AMF roots. AMF colonization significantly reduced bioactive GA3 levels by 37.9%, while it increased inactive GA8, GA9, and GA15 levels under SWD by 522.2%, 100.0%, and 2500.0%. Inoculation with AMF also up-regulated the expression of PtCPS, PtPKS, and PtKO in GA synthesis pathways of roots and the expression of PtGA20ox, PtGA3ox, and PtGA2ox in GA metabolisms under SWD. In addition, the expression of DELLA genes PtGaipb and PtGai associated with GA signaling pathways was further up-regulated under SWD by AMF inoculation. It is concluded that AMF regulated the composition, synthesis, and deactivation of GAs in roots to promote plant growth, along with an increase in PtGaipb and PtGai expression to possibly initiate mycorrhizal signaling pathways in response to SWD. •AMF boosted plant growth as well as POD and CAT activity in roots under drought.•Nine GA species were detected in roots, with GA4 only found in AMF roots.•AMF reduced GA3, but increased GA5, GA9, and GA15 levels under drought.•AMF up-regulated the expression of PtCPS, PtPKS, PtKO, PtGA20ox, PtGA3ox, and PtGA2ox under drought.•AMF increased the expression of the DELLA genes PtGaipb and PtGai under drought.