Leaf senescence is the final stage of leaf development. During leaf senescence, nutrients accumulated in mature leaves are broken down and transported to reproductive organs or actively growing young tissues. This process causes reduced photosynthesis, which impacts yield to most crops and can cause economic losses to horticultural plants and fodder plants. Therefore, understanding the detailed mechanism of leaf senescence is important to sorghum cultivation.
There is a complex interaction of environmental cues and biochemical mechanisms that underlies the chlorophyll degradation and senescence of leaves. In an effort to better understand the regulatory processes responsible for leaf senescence, researchers of Prof. Bo Sun’s group studied the WRKY TFs and signaling pathway involving the phytohormone ethylene (ET).
It is known that ET accelerates leaf senescence when applied exogenously and that inhibiting its biosynthesis or perception delays leaf senescence (Wang et al., 2001; van der Graaff et al., 2006). WRKY TFs can respond to phytohormones and have been shown to be critical for leaf senescence; however, a direct link between the WRKY TFs and ET signaling for leaf senescence has not been well established.
The present study found that SbWRKY50, a WRKY TF from Sorghum bicolor L, represses chlorophyll catabolic genes for epigenetic silencing through Polycomb repressive complex 1 recruitment and, consequently, delayed leaf senescence. SbWRKY50 overexpression delayed both age and dark induced senescence in sorghum, while early senescence resulted when SbWRKY50 was knocked out (SbWRKY5O-KO), demonstrating that SbWRKY50 is a key regulator of ethylene and leaf senescence in sorghum.
Leaf senescence is closely related to crop yield. Understanding the regulatory mechanism of leaf senescence would potentially enhance crop yield and satisfy peoples’ demand on crops. On 22th January, this finding was published on New Phytologist with the title “Ethylene-responsive SbWRKY50 suppresses leaf senescence by inhibition of chlorophyll degradation in sorghum”. Dr. Wei Chen (postdoc of Nanjing University) is the first author, and Prof. Bo Sun is the corresponding author. The work was supported by the Fundamental Research Funds for the Central Universities.
Link of the article：https://doi.org/10.1111/nph.18757