Altered Expression of the Malate-Permeable Anion Channel OsALMT4 Reduces the Growth of Rice Under Low Radiance

Abstract

We examined the function of OsALMT4 in rice (Oryza sativa L.) which is a member of the aluminum-activated malate transporter family. Previous studies showed that OsALMT4 localizes to the plasma membrane and that expression in transgenic rice lines results in a constitutive release of malate from the roots. Here, we show that OsALMT4 is expressed widely in roots, shoots, flowers, and grain but not guard cells. Expression was also affected by ionic and osmotic stress, light and to the hormones ABA, IAA, and salicylic acid. Malate efflux from the transgenic plants over-expressing OsALMT4 was inhibited by niflumate and salicylic acid. Growth of transgenic lines with either increased OsALMT4 expression or reduced expression was measured in different environments. Light intensity caused significant differences in growth between the transgenic lines and controls. When day-time light was reduced from 700 to 300 μmol m-2s-1 independent transgenic lines with either increased or decreased OsALMT4 expression accumulated less biomass compared to their null controls. This response was not associated with differences in photosynthetic capacity, stomatal conductance or sugar concentrations in tissues. We propose that by disrupting malate fluxes across the plasma membrane carbon partitioning and perhaps signaling are affected which compromises growth under low light. We conclude that OsALMT4 is expressed widely in rice and facilitates malate efflux from different cell types. Altering OsALMT4 expression compromises growth in low-light environments.

Manipulating exudate composition from root apices shapes the microbiome throughout the root system

“…Prior to this study, citrate release via TaMATE1B had only been confirmed from the seminal roots of young wheat seedlings. OsALMT4 is a member of the ALMT family of anion channels in rice, and transgenic lines over-expressing OsALMT4 display a constitutive release of malate and other substrates from the roots ( Liu et al, 2017 , 2018 ).…”

Proteomic Analysis of Rice Subjected to Low Light Stress and Overexpression of OsGAPB Increases the Stress Tolerance

“…A comparative transcriptome analysis indicated that those genes encoding some of the subunits of the light-harvesting complex, PS I and II complex are upregulated in low light-tolerant rice variety (Swarnaprabha) under low light condition compared with the low lightsensitive one (IR8) (Sekhar et al 2019). In addition, carbohydrate level and flux are also important because the altered expression of malate-permeable anion channel OsALMT4 reduces the growth of rice under low light (Liu et al 2018).…”

Brassinosteroid signaling regulates phosphate starvation‐induced malate secretion in plants

“…OsBZR1 suppressed the expression of OsALMT1 in rice There are nine putative ALMT genes in rice (Oryza sativa), and OsALMT1 and OsALMT2 have high sequence similarity to AtALMT1 (Liu et al, 2018). To test whether OsBZR1 suppresses Pi starvation-induced malate secretion in rice, we first measured OsALMT1 and OsALMT2 expression levels under Pi starvation.…”