小麦穗型相关生长素通路基因发掘及TaARF23-A与小穗数关联分析

Discovery of auxin pathway genes involving spike type and association analysis between TaARF23-A and spikelet number in wheat

生长素是调控作物穗部形态的主要内源激素之一。为了发掘小麦中与穗型相关的生长素通路基因,本研究选择了纺锤穗型品系SY95-71和密穗品系CH7034,对其幼穗内源生长素含量进行了检测,结果显示SY95-71幼穗中的色胺含量显著高于CH7034。转录组测序结果表明,在高置信区间(P<0.01)范围内, SY95-71幼穗中富集到4个特有的生长素相关条目,并且色氨酸脱羧酶基因(负责将色氨酸转化为色胺)和生长素响应因子基因(Auxin Response Factors,ARFs)的转录水平均显著高于CH7034。对在SY95-71中高表达的2个ARF基因(TraesCS7A02G475700和TraesCS7A02G475600)作了进一步分析,结果显示二者是位于7A染色体长臂上的一对串联重复基因,根据小麦ARF家族成员编号,将其分别命名为TaARF23-A1和TaARF23-A2。qRT-PCR结果证实SY95-71幼穗中TaARF23-A1和TaARF23-A2的表达量极显著高于CH7034。测序结果显示TaARF23-A的外显子序列在SY95-71和CH7034间具有2个SNP和1个InDel。根据InDel位点开发分子标记,并将其与SY95-71和CH7034的RILs群体在6个大田环境下的穗部表型进行关联分析,结果显示TaARF23-A与小穗数显著相关(P<0.0001),其CH7034型等位变异比SY95-71型等位变异增加了1.67个小穗。本研究结果将为小穗发育机制解析提供参考,也为小麦理想穗型改良提供了分子标记。

Auxin is one of the major endogenous hormones that regulate the spike morphology in crops.In order to explore the auxin pathway genes involving spike type in wheat,the line SY95-71 with spindle spike and line CH7034 with compacted spike were selected to detect the endogenous auxin content in their young spikes.The results showed that the tryptophan content in SY95-71’s young spikes was significantly higher than that in CH7034.RNA-seq results showed that four specific auxin-related GO items were enriched in SY95-71 young spikes within the high confidence interval(P<0.01),and the relative expression levels of Tryptophan Decarboxylase genes(responsible for transforming tryptophan into tryptamine)and Auxin Response Factor genes(ARFs)in SY95-71 were significantly higher than those in CH7034.Further analysis of two highly expressed ARF genes(TraesCS7A02G475600 and TraesCS7A02G475700)in SY95-71 revealed that they were a pair of tandem repeat genes located on the long arm of chromosome 7A and named TaARF23-A1 and TaARF23-A2 based on the IDs of ARF family member in wheat,respectively.The qRT-PCR results confirmed that the relative expression levels of TaARF23-A1 and TaARF23-A2 in SY95-71 young spikes were significantly higher than those in CH7034.The sequencing results showed that the exon of TaARF23-A had two SNPs and one InDel site between SY95-71 and CH7034.A molecular marker was developed based on the InDel site and then used to associated with the spike phenotypes of the recombinant inbred lines population derived by the cross of SY95-71 and CH7034 in six field environments.The results showed that TaARF23-A was significant correlation with spikelet number(P<0.0001),and its CH7034 allele increased by 1.67 spikelets compared with the SY95-71 allele.The results of this study provide the reference for the understanding of the development mechanism of spikelet and molecular marker for the improvement of ideal spike type in wheat.