Genome‐wide analysis of MADS‐box family genes during flower development in lettuce

Abstract

Lettuce (Lactuca sativa L.) is an important leafy vegetable consumed worldwide. Heat‐induced bolting and flowering greatly limit lettuce production during the summer. Additionally, MADS‐box transcription factors are important for various aspects of plant development and architecture (e.g., flowering and floral patterning). However, there has been no comprehensive study of lettuce MADS‐box family genes. In this study, we identified 82 MADS‐box family genes in lettuce, including 23 type I genes and 59 type II genes. Transcriptome profiling revealed that LsMADS gene expression patterns differ among the various floral stages and organs. Moreover, heat‐responsive cis‐elements were detected in the promoter regions of many LsMADS genes. An in situ hybridization assay of 10 homologs of flower‐patterning genes and a yeast two‐hybrid assay of the encoded proteins revealed that the ABC model is conserved in lettuce. Specifically, the APETALA1 (AP1) homolog in lettuce, LsMADS55, is responsive to heat and is specifically expressed in the inflorescence meristem and pappus bristles. The overexpression of LsMADS55 results in early flowering in Arabidopsis thaliana. Furthermore, we observed that the heat shock factor LsHSFB2A‐1 can bind to the LsMADS55 promoter in lettuce. Therefore, a model was proposed for the LsMADS‐regulated floral organ specification and heat‐induced flowering in lettuce.

A Composite Analysis of Flowering Time Regulation in Lettuce

“…The lack of clear lettuce orthologs of FLC and SVP has made it difficult to form testable hypotheses regarding the regulatory mechanism through which ambient temperatures accelerate bolting in lettuce. In addition, two studies have reported binding motifs of heat shock transcription factors in the promoter regions of LsSOC1 and LsMADS55, putative lettuce orthologs to Arabidopsis SOC1 and APETALA1 (AP1), both known to function downstream of FLC in the floral induction pathway (Chen et al, 2018b;Ning et al, 2019). These reports postulate the possibility that the thermal control of flowering time in lettuce might have a different and more concise regulatory architecture than its counterpart in Arabidopsis.…”

Mapping and identification of genetic loci affecting earliness of bolting and flowering in lettuce

“…found many genes that were differentially expressed between two lettuce cultivars with different bolting time. The authors implicated a group of MADS-box and GA genes as owering regulators (Ning et al 2019). GA and related genes were shown to be related to bolting (Fukuda et al 2009; Umetsu et al 2011) speci cally in response to high temperatures (Liu et al 2018).…”

Time-course transcriptome landscape of achene development in lettuce

“…Finally, the lettuce plants begin to bloom and bear fruit. Previously, we characterized the inflorescence development of lettuce (Chen et al, 2017), and proposed a model for lettuce floral organ specification (Ning et al, 2019). Lettuce seeds are achene fruits that are developed from the ovaries.…”