Abstract:To reveal the role of IAA and its signaling genes in the retrieved green process of pear leaves, we took chlorotic and normal plants of ‘Dangshansuli’ (Pyrus bretschneideri Rehd.) as test material. 0.2% FeSO4 solution was sprayed on the chlorotic leaves and distilled water was used for both normal and chlorotic leaves as control during the growing season. Then we observed the leaves phenotypic changes on the 3rd, 6th, 9th, and 12th day after FeSO4 application, respectively. We sampled normal, chlorotic leaves in control (CN and CC) and retrieved green leaves on the 3rd, 6th, 9th, 12th day after FeSO4 application, to determine the Fe2+ content, endogenous IAA content and IAA signaling genes expression. Furthermore, relevance analysis was performed among those indexes. The results were shown as follows: (1) application FeSO4 could convert chlorotic leaves to green, green spots appeared on the chlorotic leaves surface on 3rd day, and green plaque appeared on the both 6th and 9th day after spraying FeSO4. The whole leaves presented green on the 12th day. (2) The endogenous IAA content in CN was significantly higher than that in CC, and after spraying FeSO4, it obviously increased in retrieved green leaves compared with both CN and CC in all periods. (3) AUX1.1/1.3, GH3.1/3.2/3.5, SAUR1/2/3/4 and AUX/IAA1/2/3/7 expression in CC were prominently higher than that in CN, and most of them were notably inhibited in all period after spraying FeSO4. In contrast, TIR1.1, GH3.3/3.4 and AUX/IAA4/5/6 expression in Cc were distinctively lower than that in CN, and they were all apparently promoted by FeSO4 application. (4) ARF3/4/5/6/7/8/9/10/15/17/18/19/20/21/22/23 in Cc were clearly decreased compared with CN, and FeSO4 application significantly promoted the expression of ARF3/5/6/9/19/20/21/22/23; on the contrary, ARF1/2/11/12/13/14 were remarkably increased in Cc compared to CN, and FeSO4 application remarkably suppressed the expression of ARF1/2. (5) The relevance analysis showed that remarkably increased Fe2+ content in retrieved green leaves was positively correlated to the upregulation of AUX/IAA5 and AUX/IAA6, while IAA content was positively correlated with the increased GH3.3 expression and negatively correlated with the decreased SAUR1/2 expression. The network diagram of the association between the two above is complex, which can be simplified into Fe2+→AUX/IAA5, AUX/IAA6→(ARF14)→ARF5SAUR1, AUX/IAA1→SAUR2, TIR1.1, GH3.3→IAA. The study suggested that IAA and its signaling pathway might play a crucial role in the retrieved green process induced by spraying FeSO4 on irondeficiency chlorotic leaves of ‘Dangshansuli’ pear.