Silencing the novel gene CsARR-9 increases photosynthetic efficiency and alleviates autotoxicity in cucumber

Abstract

Autotoxicity is a principal cause of growth inhibition in monocultures. Autotoxicity in monocropped cucumber limits plant growth, which causes an obvious reduction in yield and quality in cucurbit crops. Cinnamic acid is a major autotoxin that has been used to mimic autotoxicity in cucumber. The long hairpin RNA (lhRNA) library of Arabidopsis was screened in cinnamic acid (CA) mimicked autotoxicity to obtain autotoxicity-resistant mutant lines. We found that a new gene, At5g16610, whose function is unknown, was silenced in the resistant mutant line HCA350–597, and the homologous gene of Arabidopsis At5g16610 (NM_203062.2), whose function is also unknown, was cloned in cucumber and named CsARR-9 (Cucumis sativus Autotoxicity Resistance Related). Here, we silenced the CsARR-9 gene using an established tobacco rattle virus (TRV) mediated virus-induced gene silencing (VIGS) system, and the CsARR-9 gene was also silenced by RNA interference in cucumber. We found that this silencing resulted in decreased CsARR-9 expression in both leaves and roots enhanced tolerance to autotoxicity mimicked by CA. Resistance to CA-mimicked autotoxicity was achieved by reductions in the CA concentrations in roots, stems and leaves, which maintained the structural integrity of cells and tissue within an organ system, promoted cell vigor, enhanced thylakoid stacking and increased the storage of photosynthetic products in chloroplasts, and these effects promote the growth of CsARR-9-silenced cucumber plants. These findings provide a valuable genetic resource for research regarding continuous cropping obstacles, especially in monocultures, and insights on the related molecular mechanism, and have important practical significance for prolonging the planting years and the efficient use of facility agriculture.