SlBBX20 interacts with the COP9 signalosome subunit SlCSN5-2 to regulate anthocyanin biosynthesis by activating SlDFR expression in tomato

Anthocyanins play vital roles in plant stress tolerance and growth regulation.Previously,we reported that the photomorphogenesis-related transcription factor SlBBX20 regulates anthocyanin accumulation in tomato.However,the underlying mechanism remains unclear.Here,we showed that SlBBX20 promotes anthocyanin biosynthesis by binding the promoter of the anthocyanin biosynthesis gene SlDFR,suggesting that SlBBX20 directly activates anthocyanin biosynthesis genes.Furthermore,we found by yeast two-hybrid screening that SlBBX20 interacts with the COP9 signalosome subunit SlCSN5-2,and the interaction was confirmed by bimolecular fluorescence complementation and coimmunoprecipitation assays.SlCSN5 gene silencing led to anthocyanin hyperaccumulation in the transgenic tomato calli and shoots,and SlCSN5-2 overexpression decreased anthocyanin accumulation,suggesting thSlCSN5-2 enhanced the ubiquitination of SlBBX20 and promoted the degradation of SlBBX20 in vivo.Consistently,silencing the SlCSN5-2 homolog in tobacco significantly increased the accumulation of the SlBBX20 protein.Since SlBBX20 is a vital regulator of photomorphogenesis,the SlBBX20-SlCSN5-2 module may represent a novel regulatory pathway in light-induced anthocyanin biosynthesis.

The loss of function of HEL,which encodes a cellulose synthase interactive protein,causes helical and vine-like growth of tomato

Helical growth is an economical way for plant to obtain resources.The classic microtubule–microfibril alignment model of Arabidopsis helical growth involves restriction of the appropriate orientation of cellulose microfibrils appropriately in the cell walls.However,the molecular mechanism underlying tomato helical growth remains unknown.Here,we identified a spontaneous tomato helical(hel)mutant with right-handed helical cotyledons and petals but left-handed helical stems and true leaves.Genetic analysis revealed that the hel phenotype was controlled by a single recessive gene.Using map-based cloning,we cloned the HEL gene,which encodes a cellulose interacting protein homologous to CSI1 of Arabidopsis.We identified a 27 bp fragment replacement that generated a premature stop codon.Transgenic experiments showed that the helical growth phenotype could be restored by the allele of this gene from wild-type Pyriforme.In contrast,the knockout mutation of HEL in Pyriforme via CRISPR/Cas9 resulted in helical growth.These findings shed light on the molecular control of the helical growth of tomato.

FUNCTIONAL GAIN OF FRUIT NETTED-CRACKING IN AN INTROGRESSION LINE OF TOMATO WITH HIGHER EXPRESSION OF THE FNC GENE

Fruit cracking is a major disorder that affects the integrity of fruit and reduces the commercial value of tomato and other fleshy fruit.Here,we have found a novel fruit'netted-cracking'(FNC)phenotype in tomato introgression line IL4-4 which is present in neither the donor parent(LA0716)nor the receptor parent(M82).An F2 population was generated by crossing IL4-4 with M82 to genetically characterize the FNC gene and this showed that a single dominant gene determined fruit netted-cracking.Further map-based cloning narrowed down the FNC locus to a 230 kb region on chromosome 4.Sequencing and annotation analysis show that FNC(Solyc04 g082540)was the most likely candidate gene.Functional characterization of FNC by overexpressing FNC^c and FNC1^resulted in the fruit netted-cracking phenotype,suggesting that the FNC transcript level results in the functional gain of fruit netted-cracking.These findings were further confirmed by FNC ortholog in netted-cracking pepper and melon,indicating a common regulatory mechanism in different plant species.Furthermore,cytoplasm and nucleus-localized FNC indicates increased expression of genes involved in suberin,lignin,lipid transport and cell wall metabolism.These findings provide novel genetic insights into fruit netted-cracking and offer a way to promote molecular improvement toward cracking resistant cultivars.