Six KCS genes expressed in anther of Arabidopsis
Arabidopsis genome contains 21 KCS genes. Of them,KCS1/5/6/7/9/10/11/13/15/20/21 were reported to express in flowers (Joubès et al., 2008). We performed reverse transcription-polymerase chain reaction (RT-PCR) analysis, and confirmed their expression in flowers (Fig. S1). Among them, KCS5 ,KCS7 and KCS15 were specifically expressed in flowers, while KCS6, KCS9, KCS10, KCS13, KCS20 and KCS21 were relatively highly expressed in flowers (Fig. S1). To further understand the expression patterns of these KCS proteins in the developing anthers, the KCS genomic sequences were fused to green fluorescent protein gene (GFP) to make the reporter constructs (pKCS::KCS-GFP ) to transform WT Arabidopsis plants. Transgenic lines expressingpKCS::KCS-GFP in anthers were identified (Fig.1a). The GFP signals of KCS7-GFP, KCS15-GFP and KCS21-GFP proteins displayed similar expression patterns (Fig.1a). Their GFP fluorescence was detected in tapetum at anther stage 8-10 (Fig.1a). No GFP signals were detected at stage 11 when tapetum programmed cell death (PCD) occur. The expression of these KCS s is quite similar with that of tapetal sporopollenin synthesis genes (K. Wang et al., 2018). KCS20 was expressed in tapetum at anther stage 9, and distributed within the anther locule and pollen at stage 9-11. KCS5-GFP signal was localized in epidermis at anther stages 10 to 12, while KCS10-GFP signal was preferentially detected in both epidermis and endothecium at anther stages 10 and 11 (Fig.1b).