Ruetjes, T. | Search bioRxiv

bioRxiv2025

FLOWERING LOCUS T1 is a pleiotropic regulator of reproductive development, plant longevity, and source-sink relations in barley

Source-sink interactions play a critical but mechanistically underexplored role in coordinating reproductive output and longevity in plants. Here, we investigated the role of FT1, the barley homolog of the florigen FLOWERING LOCUS T (FT), in regulating source (leaf) and sink (inflorescence) development and metabolism. Using ft1 knock-out mutants in the spring barley cultivar Golden Promise, which carries a mutated ppd-H1 allele, and in an introgression line with a wild-type Ppd-H1 allele, we show that Ppd-H1 primarily regulates the timing of inflorescence development and flowering through FT1, whereas variation in tiller number and leaf size is determined by the genetic background. ft1 mutants exhibited reduced determinacy of both leaf and inflorescence meristems, resulting in increased leaf and spikelet numbers and size, but severely reduced inflorescence fertility, altered senescence patterns, and significantly extended plant longevity. The ft1 mutants exhibited a strong transcriptional reprogramming of genes involved in both the light and dark reactions of photosynthesis in the leaf, alongside an upregulation of genes associated with carbon catabolism and stress responses in the leaf and inflorescence. Elevated soluble sugar and starch levels in ft1 inflorescences indicated that the impaired development and fertility of ft1 inflorescences were not caused by carbon limitation, but instead reflected a reduced sink strength. Our work reveals that FT1 coordinates the development of vegetative and reproductive meristems and organs with plant physiology and metabolism, thereby regulating source-sink relationships and balancing plant longevity with reproductive output.

plant biology↗

bioRxiv2023

The identification and analysis of meristematic mutations within the apple tree that developed the RubyMac sport mutation

Understanding the molecular basis of sport mutations in fruit trees can accelerate breeding of novel cultivars. For this, we analyzed the DNA of the apple tree that evolved the RubyMac phenotype through a sport mutation that introduced changes in fruit coloration in upper branches of the tree. Unexpectedly, we not only found 46 de novo mutations, but also 54 somatic gene conversions (i.e., loss-of-heterozygosity mutations) distinguishing the mutant and wild-type branches of the tree. Approximately 30% of the de novo mutations and 80% of the gene conversions were observed only in specific cells layers suggesting that they occurred in the corresponding meristematic layers. Interestingly, the de novo mutations were enriched for GC=>AT transitions, while the gene conversions showed the opposite bias for AT=>GC transitions suggesting that GC-biased gene conversions have the potential to counteract the AT-bias of de novo mutations. By comparing the gene expression patterns in fruit skins from mutant and wild-type branches, we found 56 differentially expressed genes including 18 that were involved in anthocyanin biosynthesis. While none of the differently expressed genes harbored a mutation, we found that some of the mutations affected the integrity of candidate genes in regions of the genome that were recently associated with natural variation in fruit coloration.

genomics↗