Fruit Cytological And Transcriptome Analyses And Function And Interaction Studies Of CaGID1s And CaGAI In Capsicum

Forty-nine pepper lines with varied fruit sizes and shapes selected from a recombinant inbred line (RIL) population were used in this research along with the parents and Fi hybrid. Images of pericarp cross sections revealed that pericarp (ovary wall) structures were conserved and formed before anthesis and could be easily divided into three distinguishable portions. Fruit width was correlated with ovary width, revealing the conserved nature of fruit widening. Fruit shape was not correlated with fruit cell shape, implying that cell number also affected fruit shape. With respect to fruit enlargement, fruit lengthening was allometric compared with fruit widening and pericarp thickening and cell enlargement displayed a similar pattern.Morphological and cytological dynamic growth of chile pepper fruit growth were examined using one pepper inbred line ’0819’ with elongated fruit shape. Fruit length, fruit width and fruit pericarp thickness were under similar sigmoid growth trend, and mean cell area of mesocarp in both longitudinal and transverse cross sections showed the similar growing trend. As for cell division, cells in outermost cell layer underwent anticlinal cell division at early fruit stages, and the transverse division was active before10days after pollination (DAP), promoting fruit elongation; periclinal cell division mainly occurred in outer subepidermal cell layer, and stopped before about20DAP. Cell expansion mainly occurred in mesocarp and was the main determinant factor for fruit widening, pericarp thickening and later fruit elongation.IAA, GA, ZR and ABA content of0,5,10,50DAP and5DAA-NP fruits were measured using ELISA method, and the content trend of seed and placenta were similar, while different from that of pericarp. GA content of seed at5DAP rise up, while IAA content fell down. At5DAA-NP, IAA content of seed was high, while content was low. Both of which suggesting GA may be the main regulator for fruit set, and its high content was not induced by IAA biosynthesis.Data from0,5,10and50DAP fruit RNA-seq showed that the number of expressed genes at5and10DAP was less than those of0and50DAP, revealing the simipler activities at5and10DAP than those of0and50DAP. Transcriptome data about plant growth regulators also showed that genes displayed more similar expression pattern between5and10DAP.Three GA receptors CaGID1b.1, CaGID1b.2, CaGID1c and one DELLA CaGAI were identified and cloned in Capsicum. According to gene expression analyses, it’s inferred that during fruit set CaGIDl b.2may play the most important role in growth of pericarp and placenta, while CaGID1b.1was most important in seed; during fruit development CaGID1b.1and CaGID1b.2play more important role than CaGIDlc, especially in pericarp. Ecotopical expression revealed that CaGIDls and CaGAI displayed similar function to AtGIDl and AtGAI. Y2H and BiFC assays indicated that CaGID1b.1and CaGID1b.2interact with CaGAI in a GA-dependent manner, while CaGID1c interacts with CaGAI in a GA-independent manner.