Transcriptional Programs and Regulators Underlying Age-Dependent and Dark-Induced Senescence in Medicago truncatula

Abstract

In forage crops, age-dependent and stress-induced senescence reduces forage yield and quality. Therefore, delaying leaf senescence may be a way to improve forage yield and quality as well as plant resilience to stresses. Here, we used RNA-sequencing to determine the molecular bases of age-dependent and dark-induced leaf senescence in Medicago truncatula. We identified 6845 differentially expressed genes (DEGs) in M3 leaves associated with age-dependent leaf senescence. An even larger number (14219) of DEGs were associated with dark-induced senescence. Upregulated genes identified during age-dependent and dark-induced senescence were over-represented in oxidation–reduction processes and amino acid, carboxylic acid and chlorophyll catabolic processes. Dark-specific upregulated genes also over-represented autophagy, senescence and cell death. Mitochondrial functions were strongly inhibited by dark-treatment while these remained active during age-dependent senescence. Additionally, 391 DE transcription factors (TFs) belonging to various TF families were identified, including a core set of 74 TFs during age-dependent senescence while 759 DE TFs including a core set of 338 TFs were identified during dark-induced senescence. The heterologous expression of several senescence-induced TFs belonging to NAC, WKRY, bZIP, MYB and HD-zip TF families promoted senescence in tobacco leaves. This study revealed the dynamics of transcriptomic responses to age- and dark-induced senescence in M. truncatula and identified senescence-associated TFs that are attractive targets for future work to control senescence in forage legumes.

Comprehensive transcriptomic analysis of age-, dark-, and salt-induced senescence reveals underlying mechanisms and key regulators of leaf senescence in Zoysia japonica

“…While many transcriptomic studies have identified TFs associated with leaf senescence in various non-model plants, their functional roles remain largely unknown ( Woo et al., 2013 ; Fraga et al., 2021 ; Zhang et al., 2021 ). This is because functional studies that use knock-out or transgenic approaches can be time- and resource-consuming, especially in crop species ( Mahmood et al., 2022 ). In Z. japonica , functional analyses of SAGs have been performed by transgenic approaches that introduce them in Arabidopsis.…”

“…Leaf senescence is an evolutionally acquired process that occurs during the final stage of leaf development as an energy utilization strategy ( Mahmood et al., 2022 ). Leaves are photosynthetic organs that produce chemical energy and building units for macromolecules and accumulate cellular materials during growth periods.…”

Dual RNA-Seq Analysis Pinpoints to a BalancedRegulation between Symbiosis and Immunity in the Medicago truncatula-Sinorhizobium meliloti Symbiotic Interactions

“…By genome-wide transcription profiling, symbiosis-related plant and bacterial genes can be simultaneously identified before the bacteria are physically separated from host cells. In the previous research, the expression levels of bacterial genes and host plant genes were analyzed using transcription profiling, respectively [27,28]. So far, there have been no reports on the simultaneous analyses of gene expressions of both bacteria and hosts.…”