Abstract：
The stone cells in pear fruits cause rough flesh and low juice, seriously affecting the taste. Lignin has been demonstrated as the main component of stone cells. Auxin, one of the most important plant hormone, regulates most physiological processes in plants including lignification. However, the concentration effect and regulators of auxin on pear fruits stone cell formation remains unclear. Here, endogenous indole-3-acetic acid (IAA) and stone cells were found to be co-localized in lignified cells by immunofluorescence localization analysis. The exogenous treatment of different concentrations of IAA demonstrated that the application of 200 µM IAA significantly reduced stone cell content, while concentrations greater than 500 µM significantly increased stone cell content. Besides, 31 auxin response factors (ARFs) were identified in pear genome. Putative ARFs were predicted as critical regulators involved in the lignification of pear flesh cells by phylogenetic relationship and expression analysis. Furthermore, the negative regulation of PbARF19 on stone cell formation in pear fruit was demonstrated by overexpression in pear fruitlets and Arabidopsis. These results illustrated that the PbARF19-mediated auxin signal plays a critical role in the lignification of pear stone cell by regulating lignin biosynthetic genes. This study provides theoretical and practical guidance for improving fruit quality in pear production.
摘要：
梨果实中的石细胞会引起粗糙的果肉和低汁，严重影响口味。木质素已被证明是石细胞的主要成分。生长素,最重要的植物激素之一，调节植物中的大多数生理过程，包括木质化。然而,生长素的浓度和调节剂对梨果核细胞形成的影响尚不清楚。这里,通过免疫荧光定位分析发现内源性吲哚-3-乙酸（IAA）和石细胞共定位在木质化细胞中。不同浓度的IAA的外源处理表明，200µMIAA的应用显着降低了石细胞含量，而大于500µM的浓度显着增加石细胞含量。此外,在梨基因组中鉴定出31个生长素响应因子(ARFs)。通过系统发育关系和表达分析，推定的ARFs被预测为参与梨肉细胞木质化的关键调节因子。此外，梨果实和拟南芥中的过表达证明了PbARF19对梨果实石细胞形成的负调控作用。这些结果表明，PbARF19介导的生长素信号通过调节木质素生物合成基因在梨石细胞的木质化中起关键作用。本研究为梨生产中提高果实品质提供了理论和实践指导。
