Kernel numbers per spikelet (A and B), weight per spikelet (C and D), and grain weight per spikelet (E and F) in winter wheat in growing seasons 2010/2011 (left) and 2011/2012 (right).

<p>Kernel numbers per spikelet (A and B), weight per spikelet (C and D), and grain weight per spikelet (E and F) in winter wheat in growing seasons 2010/2011 (left) and 2011/2012 (right).</p

Effect of Spikelet position on the proportion by volume distribution of starch granules in wheat grain (d.f. = 17).

<p>Means within cultivar followed by a different letter are significantly different at <i>P</i><0.05. US, Upper spikelets; MS, Middle spikelets; BS, Basal spikelets.</p><p>Effect of Spikelet position on the proportion by volume distribution of starch granules in wheat grain (d.f. = 17).</p

Mean daily temperature and sunshine durations from anthesis to maturity of wheat.

<p>Mean daily temperature and sunshine durations from anthesis to maturity of wheat.</p

Correlation coefficients between grain weight and the proportion of volume distribution and number distribution of starch granules at different spikelet positions.

<p>Correlation coefficients between grain weight and the proportion of volume distribution and number distribution of starch granules at different spikelet positions.</p

Effect of spikelet position on starch content (A) and amylase (B) accumulation in wheat grain in the growing season 2010/2011.

<p>US: Upper spikelets; MS: Middle spikelets; BS: Basal spikelets.</p

Effect of Spikelet position on starch content (A and B) and amylose content (C and D) in wheat grains in winter wheat in growing seasons 2010/2011 (left) and 2011/2012 (right).

<p>US, upper spikelets; MS, middle spikelets; BS, basal spikelets.</p

GDSL lipases modulate immunity through lipid homeostasis in rice

<div><p>Lipids and lipid metabolites play important roles in plant-microbe interactions. Despite the extensive studies of lipases in lipid homeostasis and seed oil biosynthesis, the involvement of lipases in plant immunity remains largely unknown. In particular, GDSL esterases/lipases, characterized by the conserved GDSL motif, are a subfamily of lipolytic enzymes with broad substrate specificity. Here, we functionally identified two GDSL lipases, OsGLIP1 and OsGLIP2, in rice immune responses. Expression of <i>OsGLIP1</i> and <i>OsGLIP2</i> was suppressed by pathogen infection and salicylic acid (SA) treatment. <i>OsGLIP1</i> was mainly expressed in leaf and leaf sheath, while <i>OsGLIP2</i> showed high expression in elongating internodes. Biochemical assay demonstrated that OsGLIP1 and OsGLIP2 are functional lipases that could hydrolyze lipid substrates. Simultaneous down-regulation of <i>OsGLIP1</i> and <i>OsGLIP2</i> increased plant resistance to both bacterial and fungal pathogens, whereas disease resistance in <i>OsGLIP1</i> and <i>OsGLIP2</i> overexpression plants was significantly compromised, suggesting that both genes act as negative regulators of disease resistance. OsGLIP1 and OsGLIP2 proteins mainly localize to lipid droplets and the endoplasmic reticulum (ER) membrane. The proper cellular localization of OsGLIP proteins is indispensable for their functions in immunity. Comprehensive lipid profiling analysis indicated that the alteration of <i>OsGLIP</i> gene expression was associated with substantial changes of the levels of lipid species including monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). We show that MGDG and DGDG feeding could attenuate disease resistance. Taken together, our study indicates that OsGLIP1 and OsGLIP2 negatively regulate rice defense by modulating lipid metabolism, thus providing new insights into the function of lipids in plant immunity.</p></div

Lipidomic profiling of <i>OsGLIP1/2-RNAi</i> and overexpression plants.

<p>Leaves from six individual plants (eight-week-old) were mixed as one sample from three representative transgenic lines of each transgene were used to normalize samples. Five leaf samples each genetic background were statistically analysed. (A) Total lipid composition in leaves of eight-week-old plants. (B-F) Abundance of individual lipid species, TAG (B), PA (C), MGDG (D), DAG (E) and DGDG (F). The lipid structures are presented as the number of carbon atoms: total double bonds in the fatty acyl groups. Data are shown as means ± SD (<i>n</i> = 5) of mixed leaf samples from three representative transgenic lines. *<i>P</i> < 0.05 or **<i>P</i> < 0.01, by Student’s <i>t</i>-test and Bonferroni correction for multiple (three comparisons) tests.</p

Exogenous feeding of MGDG and DGDG impairs rice disease resistance.

<p>(A) Two-week-old seedling leaves were cultured in liquid medium supplemented with MGDG or DGDG (100 μM with 0.1% Tween-20) for 24 hours. The treated plants were extensively washed and then inoculated with <i>Xoo</i> (strain PXO99A). Lesion lengths of MGDG and DGDG-fed plants were measured at 10 dpi with three biological replicates (> 10 plants each replicate). Data are shown as means ± SD from three biological replicates. (B) Bacterial growth in the MGDG and DGDG-fed plants at 0, 3 and 6 dpi, with mock treatment as control. Data are shown as means ± SD from three biological replicates. (C-E) Relative expression levels of <i>PR</i> genes <i>PR1a</i> (C), <i>PR5</i> (D) and <i>PR10</i> (E) in MGDG/DGDG treated leaves at 0 and 48 hpi. Data are shown as means ± SD from three biological replicates (<i>n</i> = 3). Student’s <i>t</i>-test, *<i>P</i><0.05, **<i>P</i> < 0.01 (A to E).</p

Proper intracellular localization is essential for OsGLIP1 function in rice defense responses.

<p>(A) Schematic diagram shows full-length OsGLIP1 with its signal peptide (SP) and the truncated protein without SP (OsGLIP1^ΔSP-GFP) or SP alone (OsGLIP1^SP-GFP) fused with GFP. (B-D) Subcellular localization of OsGLIP1 -GFP (B) OsGLIP1^ΔSP-GFP (C) and OsGLIP1^SP-GFP (D) proteins in root cells of transgenic plants. Note that removing of the signal peptide (SP) abolished OsGLIP1-GFP ER and lipid body targeting, while the SP alone was sufficient for the subcellular compartment targeting. Scale bars = 20 μm. (E, F) Deletion of the signal peptide attenuated OsGLIP1 action in suppressing plant immunity. Lesions (E) and lesion lengths (F) of representative <i>OsGLIP1-GFP</i> and <i>OsGLIP1</i>^<i>ΔSP</i><i>-GFP</i> transgenic plants inoculated with <i>Xoo</i>. Note that the OsGLIP1-GFP fusion protein also suppressed rice defense, while OsGLIP1^ΔSP-GFP lost its immune inhibition capacity. Arrows indicate bottoms of lesions. Data are shown as means ± SD (<i>n</i> > 10). Scale bar in (E) = 1cm. Student’s <i>t</i>-test, **<i>P</i> < 0.01.</p