Differential Gene Expression in the Meristem and during Early Fruit Growth of Pisum sativum L. Identifies Potential Targets for Breeding

Abstract

For successful molecular breeding it is important to identify targets to the gene family level, and in the specific species of interest, in this case <i>Pisum sativum</i> L. The cytokinins have been identified as a key breeding target due to their influence on plant architecture, and on seed size and sink activity. We focused on the cytokinin biosynthetic gene family (the <i>IPTs</i>) and the gene family key to the destruction of cytokinins (the <i>CKXs</i>), as well as other gene families potentially affected by changing cytokinin levels. These included key meristem genes (<i>WUS</i> and <i>BAM1</i>) and the transporter gene families, sucrose transporters (<i>SUTs</i>) and amino acid permeases (<i>AAPs</i>). We used reverse transcription quantitative PCR (RT-qPCR) to monitor gene expression in the vegetative meristem and in pre- and post-fertilisation young pea fruits. <i>PsWUS</i> expression was specific to the shoot apical meristem while <i>PsBAM1</i> was highly expressed in the shoot apical meristem (SAM) but was also expressed at a low level in the young fruit. Differential expression was shown between genes and within gene families for <i>IPT</i>, <i>CKX</i>, <i>SUT</i>, and <i>AAP. PsCKX7</i> showed strong gene family member-specific expression in the SAM, and was also expressed in young pea fruits. We suggest that <i>PsCKX7</i> is a potential target for downregulation via molecular breeding or gene editing.