Inhibition of strigolactones promotes adventitious root formation

Abstract

Roots that form from non-root tissues (adventitious roots) are crucial for cutting propagation in the forestry and horticulture industries. Strigolactone has been demonstrated to be an important regulator of these roots in both Arabidopsis and pea using strigolactone deficient mutants and exogenous hormone applications. Strigolactones are produced from a carotenoid precursor which can be blocked using the widely available but broad terpenoid biosynthesis blocker, fluridone. We demonstrate here that fluridone can be used to promote adventitious rooting in the model species Pisum sativum (pea). In addition, in the garden species Plumbago auriculata and Jasminium polyanthum fluridone was equally as successful at promoting roots as a commercial rooting compound containing NAA and IBA. Our findings demonstrate that inhibition of strigolactone signaling has the potential to be used to improve adventitious rooting in commercially relevant species.Adventitious root formation is the process of root initiation from a non-root tissue and the ability to induce these roots is central to plant industries worldwide. However many plant species do not readily produce adventitious roots and considerably constraining forestry and horticulture industries and limiting the use of this approach in plant conservation. Despite a long history of clonal propagation, we are only recently beginning to understand adventitious root formation at the genetic, molecular and biochemical levels. [1][2][3]

The Physiology of Adventitious Roots

“…Shoot removal by decapitation (which is often used in cutting propagation) also reduces strigolactone levels (GomezRoldan et al, 2008;Umehara et al, 2008). Inhibition of strigolactones using mutants or chemical inhibitors improved the adventitious rooting of pea and tomato cuttings (Kohlen et al, 2012;Rasmussen et al, 2012aRasmussen et al, , 2012b, and strigolactones act independently of cytokinins in intact Arabidopsis hypocotyls (Rasmussen et al, 2012b). Strigolactones may act by altering auxin transport (Bennett et al, 2006;Rasmussen et al, 2012b); however, an independent role for strigolactones on adventitious rooting cannot be fully ruled out (Rasmussen et al, 2012b).…”

Adventitious root formation in Arabidopsis : underlying mechanisms and applications

“…Increased capacity of fluridone-treated FS explants to form AR is in accordance with the findings of Rasmussen et al (2012a and b) who showed a negative influence of SL on AR formation in Arabidopsis and pea (Rasmussen et al, 2012b) as well as the stimulatory effect of fluridone on AR formation in some other plant species (Rasmussen et al, 2012a (Strader and Bartel, 2011;Kurepin et al, 2011;Schlicht et al, 2013), but other reports suggest that IBA is a biologically active entity (Ludwig-Müller, 2000). Moreover, other findings have suggested that IBA uses specific transporters for long distance transport (PDR; PLEIOTROPIC DRUG RESISTANCE family proteins; ABCG36 and ABCG37) (Strader and Bartel, 2009) and IBA is not converted to IAA during the long-distance transport (Strader and Bartel, 2011).…”

“…Similarly, it has been reported that fluridone treatment increases rooting of different plant species (Rasmussen et al, 2012a). We showed that in the light, the expression of SL biosynthesis (MAX1, MAX3 and MAX4) and signaling (MAX2) genes is increased.…”

From little things big things grow: karrikins and new directions in plant development

“…In 2008, these lines of evidence were brought together to show that strigolactones were endogenous plant hormones responsible for controlling shoot architecture (Gomez-Roldan et al 2008;Umehara et al 2008). Since this major step forward was made, strigolactones have been implicated in numerous other processes, including leaf senescence (Snowden et al 2005;Yamada et al 2014), adventitious rooting (Rasmussen et al 2012), secondary thickening (Agusti et al 2011), and regulation of root architecture under changing nutrient conditions (Ruyter-Spira et al 2011;Mayzlish-Gati et al 2012; reviewed by Al-Babili and Bouwmeester 2015; Waters et al 2017).…”