Leaf senescence is an irreversible growth process that determines plant productivity and survival, especially under environmental stress. Among water stresses, drought and submergence significantly influence senescence pathways through distinct molecular mechanisms. Drought stress accelerates leaf senescence by impairing photosynthesis, reducing leaf expansion, and disrupting water balance, with transcription factors such as NAC, WRKY, and AP2/ERF playing critical roles in its regulation. In particular, the NAC transcription factor family modulates key senescence-associated genes, while WRKY and AP2/ERF members coordinate stress responses through ABA-dependent and independent pathways. Submergence, on the other hand, induces ethylene-mediated senescence, primarily through hypoxia-induced metabolic shifts and light deprivation. ERF transcription factors, particularly ERFVII, regulate hypoxia-responsive genes, whereas bHLH and WRKY transcription factors contribute to ethylene-induced senescence. Furthermore, NAC family regulators, along with EIN3, modulate dark-induced senescence under submergence, revealing mechanistic overlap with natural senescence processes. Recent advances further reveal that epi-genetic modifications dynamically alter chromatin accessibility, activating or suppressing senescence. Moreover, posttranslational regulation through ubiquitin-proteasome degradation and autophagy modulates senescence, with the proteasome accelerating it and autophagy delaying it through selective protein turnover. This review comprehensively explores the transcriptional regulation of leaf senescence under drought and submergence stresses, along with epigenetic and posttranslational regulation, and emphasizes the role of key transcription factor families. Understanding the molecular and physiological mechanisms regulating leaf senescence under these contrasting water stresses is critical for developing stress-resilient crops and enhancing agricultural sustainability in the face of climate change.

Kaji Nemu (Citrus limon (L.) Osbeck), a unique citrus from Northeast India with extensive nutritional and therapeutic attributes, has been declared the state fruit of Assam and a geographical indication-certified commodity. Despite its known therapeutic activity, this study highlights the phytochemical potential of the methanolic peel extract of Kaji Nemu and its modulatory effects on thyroid-related pathways. The extraction yield was 10.39 %. Qualitative analysis detected tannins, alkaloids, phenols, saponins, flavonoids, terpenoids and carbohydrates. Quantitative analysis further showed that the extract contained 18.03 mg/g of total phenols, 2.25 mg/g of total flavonoids and 19.52 mg/g of total tannins. The antioxidant activity assay results showed an IC50 of 42.00 µg/mL in the DPPH assay, alongside strong FRAP and ABTS scavenging activities. The extract demonstrated cytotoxicity against HEK293 cells in the MTT assay, with an IC50 value of 177.7 µg/mL. Gas chromatography-mass spectrometry (GC-MS) analysis identified 93 phytochemicals in the extract and reported antioxidant, anti-inflammatory, anticancer and antithyroid activities. Virtual screening and molecular docking against the thyroid hormone receptor beta 1 (TRβ1) identified 3-tert-Butyl-4-hydroxyanisole, detected through GC-MS analysis, as the lead compound. It showed a strong binding affinity (-6.7 kcal/mol), which was higher than that of the reference antithyroid drug methimazole. HPLC analysis quantified vitamin E and C at 0.09 and 23.97 mg/mL, respectively, supporting its nutritional and functional value. ICP-MS mineral profiling identified sodium as the most abundant element (18.85 mg/L), followed by potassium, calcium and zinc. The study highlights the translational potential of underutilised citrus as safe, novel and effective candidates for thyroid-related treatment, meriting further mechanistic and in vivo studies.