Key <i>auxin response factor</i> (ARF) genes constraining wheat tillering of mutant <i>dmc</i>

Abstract

Tillering ability is a key agronomy trait for wheat (<i>Triticum aestivum</i> L.) production. Studies on a <i>dwarf monoculm</i> wheat mutant (<i>dmc</i>) showed that <i>ARF11</i> played an important role in tillering of wheat. In this study, a total of 67 ARF family members were identified and clustered to two main classes with four subgroups based on their protein structures. The promoter regions of <i>T. aestivum ARF</i> (<i>TaARF</i>) genes contain a large number of <i>cis</i>-acting elements closely related to plant growth and development, and hormone response. The segmental duplication events occurred commonly and played a major role in the expansion of <i>TaARFs</i>. The gene collinearity degrees of the <i>ARFs</i> between wheat and other grasses, rice and maize, were significantly high. The evolution distances among <i>TaARFs</i> determine their expression profiles, such as homoeologous genes have similar expression profiles, like <i>TaARF4-3A-1</i>, <i>TaARF4-3A-2</i> and their homoeologous genes. The expression profiles of <i>TaARFs</i> in various tissues or organs indicated <i>TaARF3</i>, <i>TaARF4</i>, <i>TaARF9</i> and <i>TaARF22</i> and their homoeologous genes played basic roles during wheat development. <i>TaARF4</i>, <i>TaARF9</i>, <i>TaARF12</i>, <i>TaARF15</i>, <i>TaARF17</i>, <i>TaARF21</i>, <i>TaARF25</i> and their homoeologous genes probably played basic roles in tiller development. qRT-PCR analyses of 20 representative <i>TaARF</i> genes revealed that the abnormal expressions of <i>TaARF11</i> and <i>TaARF14</i> were major causes constraining the tillering of <i>dmc</i>. Indole-3-acetic acid (IAA) contents in <i>dmc</i> were significantly less than that in Guomai 301 at key tillering stages. Exogenous IAA application significantly promoted wheat tillering, and affected the transcriptions of <i>TaARFs</i>. These data suggested that <i>TaARFs</i> as well as IAA signaling were involved in controlling wheat tillering. This study provided valuable clues for functional characterization of ARFs in wheat.