A KNOTTED1-LIKE HOMEOBOX Protein Regulates Abscission in Tomato by Modulating the Auxin Pathway  

Abstract

A gene encoding a KNOTTED1-LIKE HOMEOBOX PROTEIN1 (KD1) is highly expressed in both leaf and flower abscission zones. Reducing the abundance of transcripts of this gene in tomato (Solanum lycopersicum) by both virus-induced gene silencing and stable transformation with a silencing construct driven by an abscission-specific promoter resulted in a striking retardation of pedicel and petiole abscission. In contrast, Petroselinum, a semidominant KD1 mutant, showed accelerated pedicel and petiole abscission. Complementary DNA microarray and quantitative reverse transcription-polymerase chain reaction analysis indicated that regulation of abscission by KD1 was associated with changed abundance of genes related to auxin transporters and signaling components. Measurement of auxin content and activity of a DR5::b-glucuronidase auxin reporter assay showed that changes in KD1 expression modulated the auxin concentration and response gradient in the abscission zone.

Graphene oxide and indole-3-acetic acid cotreatment regulates the root growth of Brassica napus L. via multiple phytohormone pathways

“…The 2-thiobarbituric acid method [55] and TTC method [12] were used to measure the MDA content and root activity respectively. Phytohormones were extracted, purified and measured according to previously the reported methods [53,56].…”

Genome-Wide Identification of the MdKNOX Gene Family and Characterization of Its Transcriptional Regulation in Malus domestica

“…In addition, KNOX proteins are involved in other hormonal signaling pathways. KNOX change the abundance of proteins associated with auxin transporter signaling components to regulate abscission in tomato (Ma et al, 2015). Rice HOMEOBOX 1 (OSH1) represses the brassinosteroid phytohormone pathway through activation of brassinosteroid catabolism genes (CYP734A2, CYP734A4, and CYP734A6) and then arrests the growth of the SAM (Tsuda et al, 2014).…”

The legume NOOT‐BOP‐COCH‐LIKE genes are conserved regulators of abscission, a major agronomical trait in cultivated crops

“…PIN proteins are transporters of the hormone auxin that maintain auxin homeostasis in the plant and, thus, deliver positional information in many developmental processes. Interestingly, KNOX genes participate in the late stages of abscission in A. thaliana (Shi et al ., ) and S. lycopersicum (Ma et al ., ). An historical model of leaf blade abscission, based on exogenous application of auxin on debladed P. vulgaris leaf explants, proposed an auxin gradient in the leaf blade during abscission (Addicott & Lynch, ; Addicott et al ., ), whereas recently it was shown that the auxin signalling is a prerequisite for floral abscission in Arabidopsis (Basu et al ., ).…”