Transcriptomic insights into the mystery of the shield created by biogas slurry topdressing slowing maize leaf senescence

Biogas slurry (BS) up-regulated leaf photosynthetic system and chlorophyll synthesis pathway. BS increases more abundant energy for aging leaves. BS can more effectively activate the active oxygen scavenging mechanism. Premature senescence of crop foliage presents a formidable challenge to agricultural productivity. Biogas slurry (BS), an organic effluent, enhances the antioxidant defense system during leaf senescence process. However, the molecular mechanisms governing the effect of BS on maize leaf senescence remain largely unexplored. Here, we set up BS topdressing and chemical fertilizer (CF) topdressing treatments, and explored the role of BS in changing the senescence process of maize leaf through physiological and transcriptomic analyses. Our findings indicated that the BS treatment enhanced the energy supply to aging maize leaves by upreglating the expression of the photosynthetic system, promoting chlorophyll synthesis, enhancing the biological carbon fixation process, and optimizing starch and sucrose metabolism and glycolytic pathways. Furthermore, BS activated the mitogen-activated protein kinase signaling cascade and elevated peroxisomes expressions. Concurrently, it suppressed the expression of negative regulatory factors in stress-induced senescence-related plant hormones during maize maturation. Additionally, the BS treatment decreased the degradation rates of transcription factors from the WRKY, MYB, ERF, and bHLH families during maize leaf senescence. Consequently, the BS treatment reduced the average senescence rate (27.28%) and maximum senescence rate (13.94%) of leaves, and significantly increase the relative green leaf area at the full maturity stage (94.92%). Moreover, the superoxide anion content represented as a pivotal mediator in the response to leaf senescence. Thus, this study showed that BS alleviates the leaf senescence process by regulating the physiological and metabolic processes of maize, thus providing novel strategies for combating crop premature senescence.