Arabidopsis AGAMOUS Regulates Sepal Senescence by Driving Jasmonate Production

Abstract

The signal that initiates the age-regulated senescence program in flowers is still unknown. Here we propose for the ephemeral Arabidopsis thaliana flower that it dies because of continued expression of the MADS-box transcription factor AGAMOUS (AG). AG is necessary for specifying the reproductive structures of the flower. Flowers of ag-1, which lack AG, exhibited delayed sepal senescence and abscission. The flowers also had reduced jasmonic acid (JA) content. Other anther-defective sterile mutants deficient in JA, defective in anther dehiscence 1 (dad1) and delayed dehiscence 2 (dde2), exhibited delayed sepal senescence and abscission as well. Manually pollinated dad1 flowers produced siliques but still had delayed senescence, demonstrating that absence of pollination does not cause delayed senescence. When ag-1, dad1 and dde2 flowers were sprayed with 100 μM methyl jasmonate, the sepal senescence and abscission phenotypes were rescued, suggesting that JA has a role in these processes. Our study uncovers a novel role for AG in determining the timing of death of the flower it helps develop and highlights a role for JA in sepal senescence.

RNA interference suppression of AGAMOUS and SEEDSTICK alters floral organ identity and impairs floral organ determinacy, ovule differentiation, and seed‐hair development in Populus

“…Our results may be due to a role of AG in the flower senescence pathway – partially agreeing with the study done by Jibran et al . (). Alternatively, the lack of developing ovules, and the presumed hormone‐driven sink function as seeds develop (Bennett et al ., ), would be lacking in sterile catkins.…”

“…Furthermore, Jibran et al . () reported that flowers of ag mutants showed delayed sepal senescence and abscission in Arabidopsis , which could be rescued by spraying jasmonate on plants. Contrary to these findings that low AG expression retarded or prevented senescence, we noticed accelerated flower senescence in several altered RNAi events (e.g.…”

Petal abscission in fragrant roses is associated with large scale differential regulation of the abscission zone transcriptome

“…Besides ethylene and auxin, JA affects abscission of fruits, leaves and flowers, independently from ethylene 74 – 77 . JA is known to promote senescence as well as abscission 78 – 81 .…”

Micromanagement of Developmental and Stress-Induced Senescence: The Emerging Role of MicroRNAs

“…The role of TOE3 in flower patterning is not yet established [82]. Jibran et al (2017) proposed that AG functions not only in flower initiation, but also in flower development and senescence [87]. Binding AG to the ANTHER DEHISCENCE 1 (DAD1) promoter induces DAD1 gene expression to provide substrates for jasmonic acid (JA) biosynthesis.…”

“…In a senescing flower, JA regulates stamen dehiscence, sepal yellowing, and perianth abscission. Such a phenomenon is postulated to be responsible for the ephemeral phenotype of Arabidopsis flowers [87]. Ephemeral flower senescence is independent of pollination and concurrent ethylene synthesis; thus, the flower lasts less than one day [88].…”