Strigolactone signaling regulates rice leaf senescence in response to a phosphate deficiency

Abstract

Strigolactones (SLs) act as plant hormones that inhibit shoot branching and stimulate secondary growth of the stem, primary root growth, and root hair elongation. In the moss Physcomitrella patens, SLs regulate branching of chloronemata and colony extension. In addition, SL-deficient and SL-insensitive mutants show delayed leaf senescence. To explore the effects of SLs on leaf senescence in rice (Oryza sativa L.), we treated leaf segments of rice dwarf mutants with a synthetic SL analogue, GR24, and evaluated their chlorophyll contents, ion leakage, and expression levels of senescence-associated genes. Exogenously applied GR24 restored normal leaf senescence in SL-deficient mutants, but not in SL-insensitive mutants. Most plants highly produce endogenous SLs in response to phosphate deficiency. Thus, we evaluated effects of GR24 under phosphate deficiency. Chlorophyll levels did not differ of in the wild-type between the sufficient and deficient phosphate conditions, but increased in the SL-deficient mutants under phosphate deficiency, leading in the strong promotion of leaf senescence by GR24 treatment. These results indicate that the mutants exhibited increased responsiveness to GR24 under phosphate deficiency. In addition, GR24 accelerated leaf senescence in the intact SL-deficient mutants under phosphate deficiency as well as dark-induced leaf senescence. The effects of GR24 were stronger in d10 compared to d17. Based on these results, we suggest that SLs regulate leaf senescence in response to phosphate deficiency.

Strigolactone biosynthesis and signaling in plant development

“…Pea, Arabidopsis, rice and petunia mutants with defects in SL biosynthesis or SL responses were first identified based on their increased shoot branching phenotypes and their dwarfism (Beveridge et al, 1996;Ishikawa et al, 2005;Napoli, 1996;Stirnberg et al, 2002). Less obvious phenotypes, such as reduced secondary growth, delay in leaf senescence or modified root architecture, were later identified (Brewer et al, 2013;Ueda and Kusaba, 2015;Yamada et al, 2014). SLs can also modulate tolerance to abiotic stresses (drought) (Ha et al, 2014).…”

SMAX1-LIKE/D53 Family Members Enable Distinct MAX2-Dependent Responses to Strigolactones and Karrikins in Arabidopsis

“…Particularly under nutrient-poor conditions, SLs promote arbuscular mycorrhizal symbioses that enable exchange of carbon for nitrogen, phosphorus, and water (Akiyama and Hayashi, 2006; reviewed in Xie et al, 2010). Recently, SLs have been recognized as plant hormones that influence multiple aspects of development, including shoot branching (tillering), root architecture, leaf senescence, and secondary growth (GomezRoldan et al, 2008;Umehara et al, 2008;Agusti et al, 2011;Kapulnik et al, 2011;Ruyter-Spira et al, 2011;Rasmussen et al, 2012;Yamada et al, 2014;Ueda and Kusaba, 2015). SLs are synthesized from carotenoids by the DWARF27 class carotenoid isomerase and the CCD7/MORE AXILLARY GROWTH3 (MAX3) and CCD8/MAX4 classes of carotenoid cleavage dioxygenases; the sequential action of these enzymes produces carlactone (Alder et al, 2012).…”

Ecological relevance of strigolactones in nutrient uptake and other abiotic stresses, and in plant-microbe interactions below-ground

“…They play a pivotal role as modulators of the coordinated development of roots and shoots in response to nutrient deficient conditions, especially phosphorus shortage. Accordingly, SLs regulate above-and belowground plant architecture, adventitious root formation, secondary growth, reproductive development and leaf senescence (Agusti et al 2011;Gomez-Roldan et al 2008;Kapulnik et al 2011a;Kohlen et al 2012;Rasmussen et al 2012;Ruyter-Spira et al 2011;Umehara et al 2008;Yamada et al 2014). However, novel roles for SLs are emerging, for example, recently they were also shown to play a role in defence responses (Torres-Vera et al 2014).…”