| The locus sun is one of the major QTLs controlling tomato shape. Plant harboring the sun mutation produces elongated fruits, whereas the wild-type allele makes round fruits. SUN belong to the IQD gene family, which have a conservative IQ67 domain. This domain can bind to calmodulin, and up to now is only found in plant.AtIQDl is the first member of IQD family, which is found in Arabidopsis, and regulates biosynthesis of glucosinolate-a small molecule involved in plant resistant to insect. As no glucosinolate biosynthetic pathway is believed to exist in Solanaceous species, we hypothesis that function evolution may arises at thses IQD genes.We identified 17 homologues of SUN in the Nicotiana benthamiana through bioinformatics approach, and a total of 12 non-redundant putative IQD genes were extracted from these sources. After that we used real-time quantitative RT-PCR to analyse the expression profiles of the 12 IQD genes in N. benthamiana. We used the roots stems, leaves, flowers, and fruits, to research the IQD genes distribution. The results showed that they have various expression patterns. Briefly, NbTC 12223,NtEB450533,NtTC42689,NtEB441600,NbTC13078,NbTC12371,and NbTC12771 are mainly expressed in stems, suggesting that they may play roles in transportation of nutrients in plant. The NbTC11539 mainly expressed in flowers, while expressed very little in stem and leaf. In flower the the mRNA is about 16 times more than that in leaf. We also found that this gene is especially expression in the renascent tissue. So we hypothesis it may play roles in cell division. NbTC12311 expression mostly at fruit, about 16 times to the expression of root. NbEST746387 expression mostly at flower and fruit, this indicate that these two genes may play roles in reproductive growth of N. benthamiana.In order to know the function of IQD genes, we selected the NbTC11539 to do further study. We found this gene shares highly sequence homology with SUN-L13 of Solanum Lycopersicum. Then, NbTC11539 was renamed NbSUN-L13. We successful cloned the full length cDNA of NbSUN-L13 by using RACE. The gene translates a molecular mass of 58.7 kDa (518 amino acid residues) protein. It has the common feature of the IQD family, have the conserve IQ67 domain. The protein has high isoelectric point (pI-10.17) and frequency of serine residues (-11%). It contain 3 copies of the IQ motif,2 copies of the 1-5-10 motif and 2 copies of the 1-8-14 motif.We studied the effects of overexpression and RNA interference (RNAi) of this genes on the N. benthamiana. We got 7 over-expression and 8 RNAi transgenic lines. Overexpression of NbSUN-L13 displayed obvious phenotype changes in T1 transgenic plants.The renascent leaves got a little longer and narrower than their nontransgenic controls, their leaves edge became crimple, and the angle between the leaves edge and petiole get much larger. When RNAi downregulation of NbSUN-L13 expression, it has little effect on vegetative development, and this gene may play role in reproductive growth, which need further study. As NbSUN-L13 expression very little at leaves of wild type N. benthamiana, overexpressing this gene in leaves aroused its phenotype changes, while RNAi can not make significant downregulation of NbSUN-L13 at its leaf, and we did have not found obvious leaf changes at RNAi lines. |
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