AUTHOR=Xun Mi , Song Jianfei , Shi Junyuan , Li Jiaqi , Shi Yujia , Yan Junhong , Zhang Weiwei , Yang Hongqiang 

TITLE=Genome-Wide Identification of Sultr Genes in Malus domestica and Low Sulfur-Induced MhSultr3;1a to Increase Cysteine-Improving Growth

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.748242

DOI=10.3389/fpls.2021.748242

ISSN=1664-462X

ABSTRACT=<p>Sulfur is an essential nutrient for plant growth and development. Sulfate transporters (Sultrs) are critical for sulfate (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>SO</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>) uptake from the soil by the roots in higher plants. However, knowledge about Sultrs in apples (<italic>Malus domestica</italic>) is scarce. Here, nine putative <italic>MdSultrs</italic> were identified and classified into two groups according to the their phylogenetic relationships, gene structures, and conserved motifs. Various cis-regulatory elements related to abiotic stress and plant hormone responsiveness were found in the promoter regions of <italic>MdSultrs</italic>. These <italic>MdSultrs</italic> exhibited tissue-specific expression patterns and responded to low sulfur (S), abscisic acid (ABA), indole-3-acetic acid (IAA), and methyl jasmonate (MeJA), wherein <italic>MdSultr3;1a</italic> was especially expressed in the roots and induced by low S. The uptake of <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>SO</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> in cultivated apples depends on the roots of its rootstock, and <italic>MhSultr3;1a</italic> was isolated from <italic>Malus hupehensis</italic> roots used as a rootstock. <italic>MhSultr3</italic>;1a shared 99.85% homology with <italic>MdSultr3;1a</italic> and localized on the plasma membrane and nucleus membrane. Further function characterization revealed that <italic>MhSultr3;1a</italic> complemented an <inline-formula><mml:math id="M3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>SO</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> transport-deficient yeast mutant and improved the growth of yeast and apple calli under low S conditions. The <italic>MhSultr3;1a</italic>-overexpressing apple calli had a higher fresh weight compared with the wild type (WT) under a low-S treatment because of the increased <inline-formula><mml:math id="M4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>SO</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> and cysteine (Cys) content. These results demonstrate that <italic>MhSultr3;1a</italic> may increase the content of <inline-formula><mml:math id="M5" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>SO</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula> and Cys to meet the demands of S-containing compounds and improve their growth under S-limiting conditions.</p>