Ghβ-LCY1 influences metabolism and photosynthetic in Gossypium hirsutum

Carotenoids are metabolites of isoprene, which are crucial roles for plant growth and response to abiotic stress. Lycopene β-cyclase (β-LCY) is a key protease in the synthesis pathway of plant carotenoid, playing an important role in the carotenoid metabolism and synthesis pathway. However, the function of β-LCY is almost unknown in cotton (Gossypium spp.). In this study, we cloned the A and D genomes of β-LCY1 from upland cotton (Gossypium hirsutum), designated as Ghβ-LCY1A and Ghβ-LCY1D. We found that Ghβ-LCY1A and Ghβ-LCY1D were highly expressed in the cotton leaves and localized in the chloroplasts, respectively. The bacterial pigment complementarity experiment showed that Ghβ-LCY1 has the activity of β-LCY in Escherichia coli. The virus-induced gene silencing (VIGS) analysis exhibited that Ghβ-LCY1 silencing cotton plants resulted in a spotted phenotype on the leaves and sepals, slow growth, and stunted plant growth in upland cotton. Additionally, the content of chlorophyll, carotenoids, antheranthun, zeaxanthin, violaxanthin and ABA, were significantly decreased. Under normal light intensity, the chloroplast ultrastructure of leaves in Ghβ-LCY1 silencing cotton plants was abnormal, and their photosynthesis (leaf absorptance, Fv/Fm) and non-photochemical quenching (NPQ) were significantly lower than control cotton plants, and this difference was enhanced after high light treatment. Taken together, our results indicate that Ghβ-LCY1 plays an important role in carotenoids metabolism, photosynthesis and participates in plant growth and light protection in cotton.