AUTHOR=Liang Chenggang , Wei Chunyu , Wang Li , Guan Zhixiu , Shi Taoxiong , Huang Juan , Li Bin , Lu Yang , Liu Hui , Wang Yan 

TITLE=Characterization of a Novel Creeping Tartary Buckwheat (Fagopyrum tataricum) Mutant lazy1

JOURNAL=Frontiers in Plant Science

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.815131

DOI=10.3389/fpls.2022.815131

ISSN=1664-462X

ABSTRACT=<p>Gravity is known as an important environmental factor involved in the regulation of plant architecture. To identify genes related to the gravitropism of Tartary buckwheat, a creeping line was obtained and designated as <italic>lazy1</italic> from the mutant bank by <sup>60</sup>Co-γ ray radiation. Genetic analysis indicated that the creeping phenotype of <italic>lazy1</italic> was attributed to a single recessive locus. As revealed by the horizontal and inverted suspension tests, <italic>lazy1</italic> was completely lacking in shoot negative gravitropism. The creeping growth of <italic>lazy1</italic> occurred at the early seedling stage, which could not be recovered by exogenous heteroauxin, hormodin, α-rhodofix, or gibberellin. Different from the well-organized and equivalent cell elongation of wild type (WT), <italic>lazy1</italic> exhibited dilated, distorted, and abnormally arranged cells in the bending stem. However, no statistical difference of indole-3-acetic acid (IAA) levels was found between the far- and near-ground bending sides in <italic>lazy1</italic>, which suggests that the asymmetric cell elongation of <italic>lazy1</italic> was not induced by auxin gradient. Whereas, <italic>lazy1</italic> showed up-expressed gibberellin-regulated genes by quantitative real-time PCR (qRT-PCR) as well as significantly higher levels of gibberellin, suggesting that gibberellin might be partly involved in the regulation of creeping growth in <italic>lazy1</italic>. RNA sequencing (RNA-seq) identified a number of differentially expressed genes (DEGs) related to gravitropism at stages I (before bending), II (bending), and III (after bending) between WT and <italic>lazy1</italic>. Venn diagram indicated that only <italic>Pectate lyase 5</italic> was down-expressed at stages I [Log<sub>2</sub> fold change (Log<sub>2</sub>FC): −3.20], II (Log<sub>2</sub>FC: −4.97), and III (Log<sub>2</sub>FC: −1.23) in <italic>lazy1</italic>, compared with WT. Gene sequencing revealed that a fragment deletion occurred in the coding region of <italic>Pectate lyase 5</italic>, which induced the destruction of a pbH domain in <italic>Pectate lyase 5</italic> of <italic>lazy1</italic>. qRT-PCR indicated that <italic>Pectate lyase 5</italic> was extremely down-expressed in <italic>lazy1</italic> at stage II (0.02-fold of WT). Meanwhile, <italic>lazy1</italic> showed the affected expression of lignin- and cellulose-related genes and cumulatively abnormal levels of pectin, lignin, and cellulose. These results demonstrate the possibility that <italic>Pectate lyase 5</italic> functions as the key gene that could mediate primary cell wall metabolism and get involved in the asymmetric cell elongation regulation of <italic>lazy1</italic>.</p>