CnMADS1 , a MADS transcription factor , positively modulates cell proliferation and lipid metabolism in the endosperm of coconut ( Cocos nucifera L.)

Main conclusion The function of the first MADS-box transcription factor from endosperm of coconut, CnMADS1, was characterized via seed-specific overexpression in Arabidopsis seeds and further confirmed in protoplasts of coconut. Abstract Coconut ( Cocos nucifera L.), which belongs to the palm family ( Arecaceae ), is one of the world’s most useful economical tropical crops. However, few genes related to coconut endosperm development have been studied. In previous research, an AGAMOUS-like ( AGL ) MADS-box transcription factor, named CnMADS1, was identified in the endosperm of coconut through the SSH cDNA library. In this paper, functional characterization of the CnMADS1 gene was carried out by seed-specific overexpression in A. thaliana seeds and protoplasts of coconut. The results indicated that in the twelve independent T 2 transgenic Arabidopsis lines with high overexpression of CnMADS1 , the size of the mature seeds of transgenic plants was increased significantly (19.64% increase in the long axis and 8.6% increase in the short axis) compared to that of the wild-type seeds . Moreover, the total lipid content also increased significantly in mature seeds of transgenic plants . After comparing the expression of related genes in wild-type and transgenic plants and confirmation by EMSA, AtOSR1 , a regulatory gene related to seed size, was proven to be significantly up-regulated by CnMADS1 in transgenic plants. Moreover, the transient transformation of protoplasts of coconut also proved that CnLECRK3 (the homologous gene of AtOSR1 in coconut) is up-regulated by the CnMADS1 gene in the same way. All these results indicated that a similar regulation mode existed in Arabidopsis and the endosperm of coconut and ultimately affected the yield and quality of coconut copra.