Strigolactone biosynthesis in rice can occur via a 9‐cis‐3‐OH‐10′‐apo‐β‐carotenal intermediate

Abstract

Strigolactones (SLs) play a crucial role in regulating plant architecture and mediating rhizosphere interactions. They are synthesized from all‐trans‐β‐carotene converted into the intermediate carlactone (CL) via the intermediate 9‐cis‐β‐apo‐10′‐carotenal. Recent studies indicate that plants can also synthesize 3‐OH‐CL from all‐trans‐β‐zeaxanthin via the intermediate 9‐cis‐3‐OH‐β‐apo‐10′‐carotenal. However, the question of whether plants can form bioactive SLs from 9‐cis‐3‐OH‐β‐apo‐10′‐carotenal remains elusive. In this study, we supplied the 13C‐labeled 9‐cis‐3‐OH‐β‐apo‐10′‐carotenal to rice seedlings and monitored the synthesis of SLs using liquid chromatography‐mass spectrometry (LC–MS) and Striga bioassay. We further validated the biological activity of 9‐cis‐3‐OH‐β‐apo‐10′‐carotenal‐derived SLs using the ccd7/d17 SL‐deficient mutant, which demonstrated increased Striga seed‐germinating activity and partial rescue of tiller numbers and plant height. Our results establish 9‐cis‐3‐OH‐β‐apo‐10′‐carotenal as a significant SL biosynthetic intermediate with implications for understanding plant hormonal functions and potential applications in agriculture.