Photomodulation of strigolactone biosynthesis and accumulation during sunflower seedling growth

Abstract

Present investigations report the presence of strigolactones (SLs) and photomodulation of their biosynthesis in sunflower seedlings (roots, cotyledons and first pair of leaves) during early phase of seedling development. Qualitative analyses and characterization by HPLC, ESI-MS and FT-IR revealed the presence of more than one type of SLs. Orobanchyl acetate was detected both in roots and leaves. Five-deoxystrigol, sorgolactone and orobanchol were exclusively detected in seedling roots. Sorgomol was detectable only in leaves. HPLC eluted fraction from seedling roots and leaves co-chromatographing with GR24 (a synthetic SL) could also bring about germination in Orobanche cernua (a weed) seeds, which are established to exhibit SL -mediated germination, thereby indicating the SL identity of the eluates using this bioassay. SLs accumulation was always more in the roots of light-grown seedlings, it being maximum at 4 d stage. Although significant activity of carotenoid cleavage dioxygenase (CCD, the enzyme critical for SL biosynthesis) was detected in 2 d old seedling roots, SLs remained undetectable in cotyledons at all stages of development and also in the roots of 2 d old light and dark-grown seedlings. Roots of light-grown seedlings showed maximum CCD activity during early (2 d) stage of development, thereby confirming photomodulation of enzyme activity. These observations indicate the migration of a probable light-sensitized signaling molecule (yet to be identified) or a SL precursor from light exposed aerial parts to the seedling roots maintained in dark. Thus, a photomodulation and migration of SL precursor/s is evident from the present work.

Low levels of strigolactones in roots as a component of the systemic signal of drought stress in tomato

“…5. This model obviously implies that the shoot is able to discriminate between rootand shoot-produced SL; this ability needs to be proven experimentally, but could rely on differential loading in the upstream flow, and/or organ-specific production of the structurally different SL molecules, which make up species-specific SL blends and whose ecological and physiological meanings remain largely unexplored (Kohlen et al, 2011Bharti et al, 2015;Brewer et al, 2016). Alternatively, or in parallel, the uneven/ nonoverlapping distribution of the receptor protein D14 and/or of SL transporter(s) in the plant might account for discrimination between locally and distally produced SL (Chevalier et al, 2014;Sasse et al, 2015).…”

H2O2, NO, and H2S networks during root development and signalling under physiological and challenging environments: Beneficial or toxic?

“…Since nitrate deficiency influences ROS levels associated with the proliferation of root apical meristem, it would be necessary to explore strigolactone‐NO and ROS interactions in nitrate‐deficient roots (Sun et al, 2016 ). New studies on the interplay of strigolactones and H 2 S are likely to reveal their role in H 2 O 2 ‐mediated root development and signalling in plants (Bharti et al, 2015 ). Considering that ethylene has been recently known to be involved in both regulations of H 2 O 2 , and karrikin signalling (Carbonnel et al, 2020 ), it would be fruitful to consider the role of ethylene‐karrikin interaction in regulating ROS, NO, and H 2 S levels in roots.…”

“…Likewise, NO and H 2 S due to their small size and lipophilic properties can also go through the cell membranes and participate in the mechanism of the response to multiple abiotic stresses such as salinity, drought, heavy metal/metalloid stress, or anoxia (D. Piacentini, Corpas, et al, 2020;Shivaraj et al, 2019;. Similar to the aquaporin-facilitated movement of H 2 O 2 , NO and H 2 S are also involved in the transport and regulation of the aquaporin activity (Bestetti et al, 2018;Kumari & Bhatla, 2021;Liu et al, 2007;Rodrigues et al, 2017). However, unlike animal systems, less information is available on the roles of NO and H 2 S in mediating the expression and activity of aquaporins in plant roots.…”