Interspaced Repeat Sequences Confer the Regulatory Functions of AtXTH10, Important for Root Growth in Arabidopsis

Over-expression of the BnVIT-L2 gene improves the lateral root development and biofortification under iron stress

The vacuolar iron transporter (VIT) family is responsible for absorbing and storing iron ions in vacuoles. Here, the BnVIT-L2 gene from Brassica napus has been cloned for the first time and was found to be expressed in multiple tissues and organs, induced by iron stress. The BnVIT-L2 protein is located in vacuolar membranes and has the ability to bind both iron and other bivalent metal ions. Over-expression of the BnVIT-L2 gene increased lateral root number and main root length, as well as chlorophyll and iron content in transgenic Arabidopsis plants (BnVIT-L2/At) exposed to iron stress, compared to wild type Col-0. Furthermore, over-expression of this gene improved the adaptability of transgenic B. napus plants (BnVIT-L2-OE) under iron stress. The regulation of plant tolerance under iron stress by BnVIT-L2 gene may involve in the signal of reactive oxygen species (ROS), as suggested by Ribosome profiling sequencing (Ribo-seq). This study provides a reference for investigating plant growth and biofortification under iron stress through the BnVIT-L2 gene.

Reconsidering the function of the xyloglucan endotransglucosylase/hydrolase family

Plants possess an outer cell layer called the cell wall. This matrix comprises various molecules, such as polysaccharides and proteins, and serves a wide array of physiologically important functions. This structure is not static but rather flexible in response to the environment. One of the factors responsible for this plasticity is the xyloglucan endotransglucosylase/hydrolase (XTH) family, which cleaves and reconnects xyloglucan molecules. Since xyloglucan molecules have been hypothesised to tether cellulose microfibrils forming the main load-bearing network in the primary cell wall, XTHs have been thought to play a central role in cell wall loosening for plant cell expansion. However, multiple lines of recent evidence have questioned this classic model. Nevertheless, reverse genetic analyses have proven the biological importance of XTHs; therefore, a major challenge at present is to reconsider the role of XTHs in planta. Recent advances in analytical techniques have allowed for gathering rich information on the structure of the primary cell wall. Thus, the integration of accumulated knowledge in current XTH studies may offer a turning point for unveiling the precise functions of XTHs. In the present review, we redefine the biological function of the XTH family based on the recent architectural model of the cell wall. We highlight three key findings regarding this enzyme family: (1) XTHs are not strictly required for cell wall loosening during plant cell expansion but play vital roles in response to specific biotic or abiotic stresses; (2) in addition to their transglycosylase activity, the hydrolase activity of XTHs is involved in physiological benefits; and (3) XTHs can recognise a wide range of polysaccharides other than xyloglucans.

Pear xyloglucan endotransglucosylase/hydrolases PcBRU1 promotes stem growth through regulating cell wall elongation

Brassinosteroids (BRs) play numerous important roles in plant growth and development. Previous studies reported that BRs could promote stem growth by regulating the expression of xyloglucan endotransglucosylase/hydrolases (XTHs). However, the mechanism of XTHs involved in stem growth remains unclear. In this study, PcBRU1, which belonged to the XTH family, was upregulated by exogenous BL treatment in Pyrus communis. The expression of PcBRU1 was highest in stems and lowest in leaves. Subcellular localization analysis indicated that PcBRU1 was located in the plasma membrane. Furthermore, overexpressing PcBRU1 in tobaccos promoted the plant height and internode length. Electron microscopy and anatomical structure analysis showed that the cell wall was significantly thinner and the cells were slenderer in transgenic tobacco lines overexpressing PcBRU1 than in wild-type tobaccos. PcBRU1 promoted stem growth as it loosened the cell wall, leading to the change in cell morphology. In addition, overexpressing PcBRU1 altered the root development and leaf shape of transgenic tobaccos. Taken together, the results could provide a theoretical basis for the XTH family in regulating cell-wall elongation and stem growth.