The Maize glossy13 Gene, Cloned via BSR-Seq and Seq-Walking Encodes a Putative ABC Transporter Required for the Normal Accumulation of Epicuticular Waxes

Aerial plant surfaces are covered by epicuticular waxes that among other purposes serve to control water loss. Maize glossy mutants originally identified by their “glossy” phenotypes exhibit alterations in the accumulation of epicuticular waxes. By combining data from a BSR-Seq experiment and the newly developed Seq-Walking technology, GRMZM2G118243 was identified as a strong candidate for being the glossy13 gene. The finding that multiple EMS-induced alleles contain premature stop codons in GRMZM2G118243, and the one knockout allele of gl13, validates the hypothesis that gene GRMZM2G118243 is gl13. Consistent with this, GRMZM2G118243 is an ortholog of AtABCG32 (Arabidopsis thaliana), HvABCG31 (barley) and OsABCG31 (rice), which encode ABCG subfamily transporters involved in the trans-membrane transport of various secondary metabolites. We therefore hypothesize that gl13 is involved in the transport of epicuticular waxes onto the surfaces of seedling leaves.植物地上器官表面覆盖有表皮蜡质（epicuticular waxes），其生理功能之一是调控植株水分散失。最初通过"光泽"表型被筛选鉴定的玉米光泽突变体（maize glossy mutants），其表皮蜡质的积累过程会出现异常。本研究结合BSR-Seq实验数据与新开发的Seq-Walking技术，将GRMZM2G118243确定为glossy13（gl13）基因的强候选位点。多个乙基甲磺酸（EMS）诱导的突变等位基因在GRMZM2G118243中携带提前终止密码子，且gl13的一个敲除等位基因也符合该特征，这一发现验证了"GRMZM2G118243即为gl13基因"的假说。与之相符的是，GRMZM2G118243是拟南芥（Arabidopsis thaliana）AtABCG32、大麦（barley）HvABCG31以及水稻（rice）OsABCG31的直向同源基因，上述基因均编码参与多种次生代谢物跨膜运输的ABCG亚家族转运蛋白。据此我们推测，gl13参与调控表皮蜡质向幼苗叶片表面的转运过程。