Synergistic regulation of bZIP53 and dimerizing partners results in abnormal seed phenotype in Arabidopsis: Use of a designed dominant negative protein A-ZIP53

In Arabidopsis, basic leucine zipper (bZIP) family of transcription factors (TFs) are key proteins to regulate the expression of seed maturation (MAT) genes. bZIPs are functionally redundant and their DNA-binding activity is dependent on dimerization partner. The intervention of loss of function mutation is inadequate to understand and regulate the redundant behavior of TFs and one such example is bZIP53, which is known as a key regulator of seed maturation phenomena. Here, to examine the consequences of hindering the function of bZIP53 and its known and unknown heterodimerizing partners, a transgenic Arabidopsis constitutively expressing a novel dominant negative (DN) protein A-ZIP53 was raised. Transgenic plants demonstrated a delayed growth and retarded seed phenotype. The in vivo inhibition of DNA binding of bZIP53, bZIP10, and bZIP25 to the G-box demonstrated the efficacy of A-ZIP53 protein. In first generation, majority of plants failed to survive beyond four weeks suggesting a pleiotropic nature of bZIP53. Plants expressing A-ZIP53 have small flower, shorter siliques, and small-seeded phenotype. RNA seq analysis of the transgenic lines revealed the reduced expression of target genes of bZIP53 and its heterodimerizing partners. Furthermore, immunoprecipitation followed by mass spectrometry (IP-MS/MS) of transgenic plants helped to identify the additional heterodimerizing partners of the A-ZIP53. The interactions were subsequently confirmed with the transient transfection experiments. Unlike other gene knock out technologies, DN protein can inhibit the function of members of the same group of bZIP TFs.

Endosperm turgor pressure both promotes and restricts seed growth and size

Organ size depends on complex biochemical and mechanical interactions between cells and tissues. Here, we investigate the control of seed size, a key agronomic trait, by mechanical interactions between two compartments: the endosperm and the testa. By combining experiments with computational modelling, we tested an incoherent mechanical feedforward loop hypothesis in which pressure-induced stresses play two antagonistic roles; directly driving seed growth, but indirectly inhibiting it through mechanosensitive stiffening of the seed coat. We show that our model can recapitulate wild type growth patterns and explain the small seed phenotype of the haiku2 mutant. Our work further reveals that the developmental regulation of endosperm pressure is needed to prevent a precocious reduction of seed growth rate induced by force-dependent seed coat stiffening.

Evaluation of the green pea (Pisum sativum L.) collection for presence of carriers of r and rb mutations

Objective. To evaluate the green pea (Pisum sativum L.) collection in order to identify carriers of r and rb mutations in it. Methods. Pea accessions were grown in the field, and seeds were produced under controlled pollination. The starch granule shape was determined in micrographs taken with a computer digital microscopic camera DMC-300 through a Biolam-15 microscope (object lens × 40). The starch content was determined polarimetrically by the Evers method and the amylase content colorimetrically — by the BO Juliano method. The data were statistically processed using analysis of variance. Results. The effect of r and rb mutations on the starch content and fractional composition in pea seeds was confirmed. In smooth-seed accessions the average starch content was 39,9 %, and the amylose content in starch was 45,9 %, while in r mutation carriers these contents were 31 ,2 % and 67,6 %, respectively, and in rb mutation carriers — 26,9 % and 28,2 %, respectively. An accession with marrowfat seeds, roundish starch granules and a low content of amylose in starch was identified. It was established that this accession was a carrier of a recessive mutation that is not allelic to r mutation and coincides with rb mutation by the effect type. Conclusions. A new genetic source of starchmodifying monogenic rb mutation of pea was identified. It was involved hybridization with sources of r mutation to expand the genetic basis of pea cultivar breeding.Keywords: peas, Pisum sativum, genetic diversity, r, rb, seed phenotype, starch grain shape, starch content, amylose content.

Culinary and sensory traits diversity in the Spanish Core Collection of common beans (Phaseolus vulgaris L.)

<p>The Spanish National Plant Genetic Resource Center’s core collection of bean germplasm includes 202 accessions selected from more than 3000 accessions in function of passport data, seed phenotype, genetic background, and agronomic traits. To acquire more useful information about these accessions, we cultivated and characterized them for sensory and culinary traits. We found considerable variation for culinary and sensory traits of the cooked beans (mean coefficients of variation: 41% for the sensory traits and 40% for the culinary traits). The large dataset enabled us to study correlations between sensory and culinary traits and among these traits and geographic origin, seed color, and growth habit. Greater proportion of white in the seed coat correlated positively with brightness and negatively with mealiness (r=0.60, r=-0.60, <em>p</em>&lt;0.001, respectively). Mealiness correlated negatively with seed-coat roughness and rate of water absorption (r=-0.60, r=-0.53, <em>p</em>&lt;0.001, respectively). Materials of Andean origin had lower seed-coat brightness (<em>p</em>&lt;0.01) and seed-coat roughness, and greater seed-coat perceptibility, mealiness, flavor, and aroma (<em>p</em>&lt;0.001) than materials of Mesoamerican origin. Growth habit failed to correlate with culinary or sensory traits. Breeders can benefit from the information about this core collection available at <a href="http://wwwsp.inia.es/Investigacion/centros/crf/BasesDatos/Bases">www.crf.inia.es/crfesp/paginaprincipaljudia</a>.asp.</p>