Grafting semi-wild tomato GZ-05 rootstocks improved cold tolerance via the signalling of melatonin and jasmonic acid

Abstract

Tomato (Solanum lycopersicum) cultivation in the off-season is significantly hindered by cold stress; hence, utilising stress-resistant rootstocks in grafting is a critical solution. This study used 30 semi-wild tomato GZ-05 plants as rootstocks and Ailsa Craig (AC) tomatoes as scions. After cold stress, the scion tolerance index, leaf ion permeability, and other physiological and biological indicators were used to determine the most tolerant plants. To understand the molecular basis of GZ-05 rootstock cold stress resistance, RNA sequencing and reverse transcription polymerase chain reaction techniques were used to compare the varying genes expressed in the grafted AC/GZ-05 and self-grafted AC/AC plant scion leaves. The results indicated that genes associated with melatonin (MT) and jasmonic acid (JA) production and their signalling pathways were considerably altered. The initial MT and JA levels in the GZ-05-grafted plant scions were high, and when they were exposed to cold stress, the amount of active MT and JA in AC/GZ-05 heterologous grafts were great. Using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9, we knocked out the MT synthesis gene (SlCOMT14) and JA synthesis gene (SlLoxD) and found that GZ-05 plant cold stress tolerance decreased. External tests were conducted to evaluate the GZ-05 SlCOMT14 and SlLoxD knockout lines. Source spraying with MT and methyl jasmonate showed that knockout strain cold stress tolerance could be recovered. SlICE1, a tomato cold stress tolerance transcription factor, was silenced, resulting in decreased tolerance to MT- and JA-induced cold stress. The MT/JA-inducer of C-repeat binding factor (CBF) expression 1-CBF pathway may be the mechanism by which the semi-wild tomato GZ-05 rootstock confers cold tolerance to plants. This study has uncovered the molecular mechanism by which grafting semi-wild tomato GZ-05 rootstocks increases plant cold tolerance, thereby laying the groundwork for the utilisation of Guizhou's native semi-wild tomato germplasm resources.