AUTHOR=Rychel-Bielska Sandra , Plewiński Piotr , Kozak Bartosz , Galek Renata , Ksia̧żkiewicz Michał 

TITLE=Photoperiod and Vernalization Control of Flowering-Related Genes: A Case Study of the Narrow-Leafed Lupin (Lupinus angustifolius L.)

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.572135

DOI=10.3389/fpls.2020.572135

ISSN=1664-462X

ABSTRACT=<p>Narrow-leafed lupin (<italic>Lupinus angustifolius</italic> L.) is a moderate-yielding legume crop known for its high grain protein content and contribution to soil improvement. It is cultivated under photoperiods ranging from 9 to 17 h, as a spring-sown (in colder locations) or as an autumn-sown crop (in warmer regions). Wild populations require a prolonged cold period, called vernalization, to induce flowering. The key achievement of <italic>L. angustifolius</italic> domestication was the discovery of two natural mutations (named <italic>Ku</italic> and <italic>Jul</italic>) conferring vernalization independence. These mutations are overlapping deletion variants in the promoter of <italic>LanFTc1</italic>, a homolog of the <italic>Arabidopsis thaliana FLOWERING LOCUS T</italic> (<italic>FT</italic>) gene. The third deletion, named here as <italic>Pal</italic>, was recently found in primitive germplasm. In this study, we genotyped <italic>L. angustifolius</italic> germplasm that differs in domestication status and geographical origin for <italic>LanFTc1</italic> alleles, which we then phenotyped to establish flowering time and vernalization responsiveness. The <italic>Ku</italic> and <italic>Jul</italic> lines were vernalization-independent and early flowering, wild (<italic>ku</italic>) lines were vernalization-dependent and late flowering, whereas <italic>the Pal</italic> line conferred intermediate phenotype. Three lines representing <italic>ku</italic>, <italic>Pal</italic>, and <italic>Ku</italic> alleles were subjected to gene expression surveys under 8- and 16-h photoperiods. <italic>FT</italic> homologs (<italic>LanFTa1</italic>, <italic>LanFTa2</italic>, <italic>LanFTc1</italic>, and <italic>LanFTc2</italic>) and some genes selected by recent expression quantitative trait loci mapping were analyzed. Expression profiles of <italic>LanFTc1</italic> and <italic>LanAGL8</italic> (<italic>AGAMOUS-like 8</italic>) matched observed differences in flowering time between genotypes, highlighted by high induction after vernalization in the <italic>ku</italic> line. Moreover, these genes revealed altered circadian clock control in <italic>Pal</italic> line under short days. <italic>LanFD</italic> (<italic>FD</italic>) and <italic>LanCRLK1</italic> (<italic>CALCIUM/CALMODULIN-REGULATED RECEPTOR-LIKE KINASE 1</italic>) were negatively responsive to vernalization in <italic>Ku</italic> and <italic>Pal</italic> lines but positively responsive or variable in <italic>ku</italic>, whereas <italic>LanUGT85A2</italic> (<italic>UDP-GLUCOSYL TRANSFERASE 85A2</italic>) was significantly suppressed by vernalization in all lines. Such a pattern suggests the opposite regulation of these gene pairs in the vernalization pathway. <italic>LanCRLK1</italic> and <italic>LanUGT85A2</italic> are homologs of <italic>A. thaliana</italic> genes involved in the <italic>FLOWERING LOCUS C</italic> (<italic>FLC</italic>) vernalization pathway. Lupins, like many other legumes, do not have any <italic>FLC</italic> homologs. Therefore, candidate genes surveyed in this study, namely <italic>LanFTc1</italic>, <italic>LanAGL8, LanCRLK1</italic>, and <italic>LanUGT85A2</italic>, may constitute anchors for further elucidation of molecular components contributing to vernalization response in legumes.</p>